Homework Help for Physics

physics

Motion And Energy

Objectives:

• identify properties of matter and energy and describe the interactions between them

• describe a frame of reference

• describe the relationship between speed, distance, and time

• describe the difference between constant and average speed

• understand the difference between positive and negative acceleration

• understand the difference between potential and kinetic energy

Directions: Read the lesson and complete the Practice Activities, but submit only the Review questions for grading.

Introduction

This lesson will help you understand the concept of motion and energy through the use of speed, distance, and time. How are the concepts of speed, distance, and time related to each other and to motion?

Vocabulary

• energy

• potential energy

• kinetic energy

• conservation of energy

• acceleration

• speed

• distance

• time

Physics Concepts and Terms

Motion is relative. That means that how you perceive a moving object depends on your frame of reference. You see from this link that motion is dependent on the observer's frame of reference. Here is another example: Two men are at a train station. One man is on the train, and the other is standing on the platform. The train moves away. The man on the platform sees the man on the train as moving. The man in the train sees himself as being still and the man on the platform is seen as moving away.

MEASURING MOTION: Motion is measured in speed and velocity. Speed is the distance or how far an object travels in a certain amount of time. The formula for speed is speed = distance/time or s=d/t. Speed is usually expressed in kilometers per hour. Our country's method of measuring speed is expressed in miles per hour. Velocity is the speed plus the direction of an object's motion. Velocity measures the rate of change in an object's position.

Constant speed means that an object's speed does not change at all! Constant speed means that equal distances are covered in equal amounts of time. On a graph, the curve for a constant speed appears as a straight line.

Average speed is calculated as the total distance traveled divided by the total time of travel.

FORMULAS TO REMEMBER

**Hint: remember the "relative" relationship between multiplication and division, to help you use these formulas. (for example: 6 = 3 x 2, 2 = 6/3, 3 = 6/2)**

Speed = distance/time, s = d/t

Time = distance/speed, t = d/s

Distance = speed x time, d = st

Practice Problem:

A car travels 120 km in 1250 seconds. What is the speed in kph?
Use the GUESS system: Given, Unknown, Equation, Set up, and Solve.

Given: distance = 120 km and time = 1250 seconds. To get time in hours convert the seconds by dividing. 60 seconds = 1 minute. 60 minutes = 1 hour. 60 x 60 = 3600 seconds in one hour. 1250/3600 = 0.347 hours.
Unknown: speed in kilometers
Equation: s = d/t
Set up: s = 120 km / 0.347 hours

Solve: 345.82 kph

Acceleration is the rate at which changes in velocity occur. A positive acceleration means that speed continually increases. Negative acceleration means that the object is continually moving slower or is decelerating.

Here is the formula for acceleration: acceleration = (final velocity - starting velocity) divided by time.

Practice Problem: What is the acceleration of a car which starts from a stop and reaches a speed of 72 kph in 10 seconds?

Given: Vf = 72 kph, Vi = O kph, and time is 10 sec.
Unknown: Acceleration
Equation: a = (Vf - Vi)/t
Set up: a = ( 72 - 0)/10
Solution: Acceleration is equal to 7.2 kph/s

• If the acceleration is negative acceleration, a negative sign must appear before the answer.
• An object moving in a circle changes direction so it accelerates. This type of acceleration is called "centripetal acceleration."

ENERGY AND CHANGE: Any change in motion requires energy.

Energy is the ability to do work and is the source of change.

Potential energy is stored energy or the energy of position. Potential energy is usually written as P.E. If an object is sitting still, it has potential energy.

Kinetic energy is the energy of motion and is usually written as K.E. The amount of kinetic energy depends on the moving object's mass and speed. The formula for K.E. is: K.E. = (mass x the velocity squared) divided by 2.

Conservation of Energy states that energy cannot be created or destroyed but can be changed into other forms.

When we observe our surroundings, we can see many physical interactions taking place around us like a book falling, an eardrum vibrating, bus moving, nuclear reactions, etc. Everything in the universe moves. It can either be a small amount of movement or swift, but the movement does happen. This change in the position of an object is called Motion.

If an object is moving, we would be curious to know what are the things happening that make a body move, how long will a body move, and many other queries pop in.

An object tends to continue in its motion at a constant velocity until and unless an outside force acts on it. The term velocity refers both to the speed and the direction in which an object is moving. It is easy to recognize an object in motion and an object at rest. One must apply an external force to disrupt the balance. The following are the terms to be recognized before learning Motion:

• Rest: When the body does not change its position with respect to the surroundings, the body is said to be at rest.

  • Motion and Rest are relative terms.

    Examples:

• The person sitting inside the moving train is at rest, whereas the person sitting next to him but who is at Motion with the person outside the moving train.
• A book on the table is at rest with respect to the table and other objects in the room. But all these objects are sharing the motion of the earth

Or

• A car moving on a road is said to be in motion compared to the poles and trees on the roadside. But the people sitting inside the car are at rest compared to one another.

What is Motion?
Motion is a change in position of an object or else a process of moving or being moved. When the body changes its position with respect to its surrounding, the body is said to be in Motion.

• Examples: A football on the ground, the motion of the moon around the earth, a rock falling off a cliff, a car moving on the road to trees on the roadside, the person inside a moving bus with respect to a person outside the bus, a bird flying in the sky are the examples of motion.

Distance and Displacement
The minimum distance between two points is called displacement while the actual path covered is called distance. The displacement is a vector term and distance is a scalar term. Distance and displacement both have SI units as meters.

Displacement vector
Consider a trapezoid with angles A, B, and C.

AB + BC = distance moved and AC = displacement

The effect of AB + BC is the same as the effect of AC.

On one round trip, the distance is 2(AB + BC) while the displacement = AC + CA = 0 Hence the distance is never zero while the displacement is zero in one round trip. As we know that the rate of change of displacement is velocity similarly we have,

• The SI unit for velocity and speed is meter/second (m/s).
• The speed is a scalar term and velocity is a vector term.
• The speed cannot be zero since distance cannot be zero while the velocity can be zero as displacement can be zero.

• Speed = Distance moved / Time taken = S = d / t

  where d is the distance moved.

Types of Motion
The types of motion are:

• Uniform motion

• Non-uniform motion

  a) Uniform motion: When the equal distance is covered in an equal interval of time, the motion is said to be in uniform motion. The bodies moving with constant speed or velocity have a uniform motion or increase at the uniform rate.

  

   

  b) Non-Uniform motion: When unequal distances are covered in an equal interval of time, the motion is said to be in non-uniform motion. The bodies executing non-uniform motion have a varying speed or velocity.

We can even classify motion into three types:

• Translatory motion

• Rotatory motion

• Vibratory motion

Translatory Motion
In Translatory motion, the particle moves from one point in space to another. This motion may be along a straight line or along a curved path. They can be classified as:

• Rectilinear Motion - Motion along a straight line is called rectilinear motion.
• Curvilinear Motion - Motion along a curved path is called curvilinear motion.

• Rotatory Motion - In Rotatory motion, the particles of the body describe concentric circles about the axis of motion.
• Vibratory Motion - In Vibratory motion, the particles move to and fro about a fixed point.

Equations of Motion
The variable quantities in a uniformly accelerated rectilinear motion are time, speed, distance covered, and acceleration. Simple relations exist between these quantities. These relations are expressed in terms of equations called equations of motion.

There are three equations of motion.

1) v = u+at

2) S = ut + 1/2 at2

3) v2 = u2 + 2as

• Where,

v = Final Velocity
u = Initial velocity
a = acceleration
s = distance traveled by a body
t = time taken.

Derivation of Equation of Motion
First Equation of Motion:
Consider a particle moving along a straight line with a uniform acceleration 'a'. At t=0, let the particle be at A and u be its initial velocity, and when t=t, V be its final velocity.

First Equation of Motion
Acceleration = change in velocity / Time
= v-u / t
at = v-u
v = u+ at ........ First equation of motion.

Average Velocity = Average Velocity = .....

(1)Average Velocity can be written as Average Velocity = ........
(2)From equations (1) and (2) = .......
(3)The first equation of motion is v = u + at.

Substituting the value of v in equation (3) we get:

Second Equation of Motion:

Total distance traveled / Total time taken
s / t

u + v / 2
u + v /2

s / t = u + v / 2

s / t = u + u + at) / 2

s = (2u + at)t / 2 = 2ut + at2 / 2 = 2ut /2 + at2 / 2
Which gives the second equation of motion.

Third equation of Motion:

The first equation of motion is v = u + at.

v - u = at ... (1)

Average velocity = s / t ... (2)

Average velocity = u+v / 2 ... (3)

From equation (2) and equation (3) we get,

u+v / 2 + st ... (4)

Multiplying eq (1) and eq (4) we get,

(v - u)(v + u) = at x 2s / t
(v - u)(v + u) = 2as

We make use of the identity a2 - b2 = (a + b) (a - b)

v2 - u2 = 2as.......................... Third equation of motion.

Angular Motion
Motion can be angular or uniform. When the body moves on a curved path, there is a change in angular displacement, this is called an angular motion. The rate of change of angular displacement gives angular velocity. It’s a vector term.

• The angular motion is always an accelerated motion.

  • Angular velocity (ω) = dθ / dt

    Where theta is angular displacement.

Uniform Motion
When the body moves in a straight path, an equal change in linear displacement in an equal interval of time gives uniform motion.

• Uniform velocity (v) = dS / dt

  Where dS is the change in linear di.

Practice Activity 1 - Distance, Speed, Acceleration

Directions: Use the equation above to answer the following questions. Do not submit for grading.

1. A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast (what speed) were they running?

2. The pitcher’s mound in baseball is 85 m from the plate. It takes 4 seconds for a pitch to reach the plate. How fast is the pitch?

3. If you drive at 100 km/hr for 6 hours, how far will you go?

4. If you run at 12 m/s for 15 minutes, how far will you go?

5. Every summer I drive to Michigan. It is 3900 km to get there. If I average 100 km/hr, how much time will I spend driving?

6. A bullet travels at 850 m/s. How long will it take a bullet to go 1 km?

7. Every winter I fly home to Michigan. It takes 5 hours. What is my average speed?

8. The fastest train in the world moves at 500 km/hr. How far will it go in 3 hours?

9. How long will it take light moving at 300,000 km/s to reach us from the sun? The sun is 15,000,000 km from earth.

10. It is 21,000 kilometers around the earth and the earth rotates in 24 hrs. How fast is it rotating?

11. A car goes from 0 to 100 km/hr in 10 seconds. What is its acceleration?

12. A bus slams on its breaks and goes from 30 km/hr to 15 km/hr in 4 seconds. What is its acceleration?

Practice Activity 2 - Distance and Displacement

Directions: For each question plot the path on the grid paper.

1. Joey drives his Skidoo 7 kilometers north. He stops for lunch and then drives 5 kilometers east. What distance did he cover? What was his displacement?

2. Anthony walks to the pizza place for lunch. He walks 1 km east, then 1 km south, and then 1 km east again. What distance did he cover? What was his displacement?

3. On his fishing trip Justin takes the boat 12 km south. The fish aren’t biting so he goes 4 km west. He follows a school of fish 1 km north. What distance did he cover? What was his displacement?

4. Preston goes on a camel safari in Africa. He travels 5 km north, then 3 km east, and then 1 km north again. What distance did he cover? What was his displacement?

5. Neil pogo sticks to his science class. He travels 8 m east the 4 m north. What distance did he cover? What was his displacement?

Practice Activity 3 - Displacement, Velocity, Acceleration

Directions: Determine the following answers. Do not submit for grading.

1. A person starts at a position of 5.0km East of his house. After running for a period of time, he undergoes a displacement of 2.3km {East}. What is his new position?
2. A person is driving a car along a straight highway. The car’s position at 9:00 am is 13 km to the East of his home. The car’s position at 10:30 am is 137km to the East of his home. What is the displacement of the car?
3. A delivery person drives 83km North to pick up a package. Then he drives 34km South to deliver the package.

a) What was the delivery person’s distance traveled?
b) What was the delivery person’s displacement?

Practice Activity 4 - Speed and Velocity (constant motion)

Directions: Determine the following answers. Do not submit for grading.

1. A person walks 5.0km in 2.00h. Then he walks 1.5km in 0.50h. Finally he walks 10.0km {East} in 2.25h.

a) What is the person’s average speed for the journey?
b) What is the person’s average velocity for the journey?
c) What is the person’s instantaneous velocity at 1.00h?
d) What is the person’s instantaneous velocity at 2.25h?

2. A person drove 4.0km {North} and then 6.4km {South}.

a) If the person’s average speed was 65 km/h, how long did the trip take?
b) What was the person’s average velocity?

3. A person starts from home and drives with a velocity of 55km/h {East} for 30 minutes. The person then drives with a velocity of 73km/h {West} for 45 minutes. Where is the person now?
4. Two people start at the same location. One person jogs with a velocity of 3.5m/s {East} for 30 minutes. The other jogs with a velocity of 1.5m/s for 45 minutes. Where is each person? How far apart are they?
5. You plan a 200. km trip on which you want to average a speed of 90. km/h. You cover the first half of the distance at an average speed of only 48km/h. What must your average speed be in the second half of the trip to meet your goal?

Practice Activity 5 - Basic Word Problems for Acceleration (constant acceleration)

Directions: Answer each of the following questions. Do not submit for grading.

1. Myriam Bédard accelerates at an average of 2.5 m/s2 for 1.5 s. What is her change in speed at the end of 1.5 s?
2. A skateboarder rolls down a hill and changes his speed from rest to 1.9 m/s. If the average acceleration down the hill is 0.40 m/s2, for how long was the skateboarder on the hill?
3. Kerrin Lee-Gartner is moving at 1.8 m/s near the top of a hill. 4.2 s later she is traveling at 8.3 m/s. What is her average acceleration?
4. A bus with an initial speed of 12 m/s accelerates at 0.62 m/s2 for 15 s. What is the final speed of the bus?
5. A snowmobile reaches a final speed of 22.5 m/s after accelerating at 1.2 m/s2 for 17 s. What was the initial speed of the snowmobile?

Lesson Review

Directions: Answer each of the following questions. Remember to cite your resources. Citation examples are provided below the Review.

1. What would a graph of the speed of an object that moves at a constant speed look like? (hint: curved line, broken line, etc.)

2. A car travels 120 km in 1250 seconds. What is the speed in kilometers per hour?

3. A kayak races 100 meters in 50 seconds. What is the speed of the kayak?

4. How far would you travel moving at 12 m/s for 3.00 minutes?

5. How long would it take to travel 50 km traveling at a speed of 10 km/hr?

6. What is the best definition for a frame of reference?

7. You ride the bus home each day. It takes 45 minutes to travel 100 kilometers. What is the speed in kph?

8. What is the acceleration of a rocket whose velocity increases from 15.0m/s to 45.0 m/s in 2 seconds?

9. What is a good definition for the Conservation of Energy?

10. An airplane taking off increases its velocity from 10.0m/s to 100.0m/s in 2.0 seconds. What is the acceleration?

11. Two cars, A and B, are 400 meters apart. Car A travels due east at 30 meters per second on a collision course with car B, which travels due west at 20 meters per second. How much time elapses before the two cars collide?

12. The amount of kinetic energy an object has depends on what?

13. What is the acceleration of a train that starts from rest and reaches the speed of 105m/s in 30.0 seconds?

14. The speed of a car is decreased uniformly from 30 meters per second to 10 meters per second in 4.0 seconds. What is the magnitude of the car's acceleration?

15. A moving object that does not vary its speed is said to be moving at average velocity, constant velocity, average speed, constant speed, or equilateral speed? Explain your answer.

physics

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Mechanics - Fundamental Quantities

Objectives:

• identify properties of matter and energy and describe the interactions between them

• describe energy/matter and their various forms and relationships

• describe interactions of two or more things and the effect each has on the other

• understand cause and effect relationships that allow predictions to be made

Directions: Read the lesson and complete the Review.

Introduction

The mechanics used in the study of Physics is important to a thorough understanding of the subject matter. In this lesson module, you will learn the fundamental quantities used in Physics.

Vocabulary

• piezoelectric

• synchronous

• pendulum

• sidereal

• ecliptic

• ambiguity

• parsec

• subtends

Physics

Physics takes its place among the physical sciences with astronomy, chemistry, and geology, in dealing with natural phenomena concerning the behavior of inanimate objects, and some of its principles apply to living things as well. The fields of knowledge of these sciences overlap considerably and give rise to such branches as astrophysics, physical chemistry, geophysics, and biophysics. The laws and facts of Physics are concerned broadly with matter and energy, together with such related quantities as force and motion. These concepts and their inter-relations are fundamental to all parts of the subject, comprising mechanics of solids and fluids, heat, electricity and magnetism, sound, and light.

A definite knowledge of natural phenomena, and of the precise relations between them, is based upon experimental information concerning the quantities involved. If this information should be indefinite or ambiguous it would be subject to different interpretations, and naturally, the conclusions drawn therefrom would be open to much speculation. Clearly, the evidence obtained must be quantitative in order that it may have a definite meaning. Evidence of this type is obtained by measurement, one of the most important elements in all scientific work.

The usual way to measure a quantity is to compare it with some other quantity of the same kind which is used as a basis of comparison. Everyone is familiar with the process of measuring the length of an object by laying a foot-rule alongside it and expressing the result in feet and inches. A statement that a pole is 15 feet in length will give anyone having a foot-rule a correct picture of that length by laying off a distance equal to 15 one-foot distances. The length of the pole can also be expressed as 180 inches. This illustration shows that the measurement of a quantity involves two things; a number and a unit.To say that the pole measures 15 or 180 is an incomplete statement; it is necessary to say 15 feet or 180 inches. The unit shows how large a quantity is used as the basis of comparison, and the number shows how many of these units are contained in the quantity being measured.

Some statements based on physical measurements are given below to indicate the necessity for both number and unit: The rating of a certain automobile engine is 65 horsepower. The speed of a large steamship was found to be 25.3 knots. A Comfortable room temperature is 68 degrees Fahrenheit. Atmospheric pressure is about 14.7 pounds per square inch. The angular speed of a particular motor is 1800 revolutions per minute. The wavelength of yellow light is 0.0000589 centimeters. The charge of an electron is 1.60 X 10-19coulomb.

Physics is called an exact science because the quantities with which it is concerned are capable of accurate measurement. Accuracy in measurement requires knowledge of the correctness of the standard comparison, a measuring device of adequate sensitiveness, and care on the part of the operator in manipulation and computation.

Among the quantities which Physics deals, three are generally regarded as fundamental, namely, length, mass, and time.

Standards and Units of Length
The units of length commonly used belong to two groups, namely British Units and Metric Units, and these are based upon definite distances on bars that are preserved as standards. The yard is the standard length in the British group and is the distance at 62 degrees Fahrenheit (oF.) between two fine lines engraved on gold plugs in a bronze bar kept at the Standards Office in Westminster, London. The meter is the standard of length in the Metric Group and is the distance at degree centigrade (oC.) between the centers of two lines traced on a platinum-iridium bar kept in a subterranean vault of the International Bureau of Weights and Measures at Sevres, France. Several such standards are kept at the Bureau of Standards in Washington, D.C.

The multiples and sub-multiples of the yard and of the meter in common use are given below with their equivalents for reference purposes:

It is often necessary to convert expressions of length in one group to corresponding ones in the other group. The fundamental relationship between the yard and the meter, as fixed by the Act of 1866, is 1 yard = 3600/3937 meter. In consequence, the relations given above hold with sufficient exactness for most purposes.

At least the two relationships should be remembered.

In carrying out a computation involving lengths or other physical quantities, the units should be included throughout; they may be canceled, multiplied, or divided as though they were numbers. For example, find the number of kilometers in a mile by using the conversion factor 1 meter = 39.37 in. Since 5280 feet = 1 mile, the fraction 5280 feet/1 mile will have a value of unity, and the specified distance may be multiplied by this factor without altering its value. Three other fractions, each having a value of unity, are introduced in the same manner, and the entire solution is given by:

This procedure may seem laborious for such a simple computation, but in the more involved calculations, there is a distinct advantage in carrying all units through to avoid ambiguity and error.

Mass and its Measurement
It is assumed that all matter is composed of extremely small particles called molecules. All the molecules of a particular substance are, in general, alike and each consists of a definite structure of component parts; the structure of a molecule of one substance will, however, differ from that of another substance. Consequently, any particular object is composed of a definite quantity of matter determined by the number of molecules it contains and by the structure of the molecules themselves.

The term mass will be used for the present as a measure of the quantity of matter in a body. The British and Metric standards of mass are:

The kilogram of mass is defined as the mass of a certain block of platinum preserved at the International Bureau of Weights and Measures and known as the standard kilogram.

Other units of mass and the relations between them appear in the following table:

The measurement of mass is usually accomplished with an equal-arm balance, the mass to be measured is placed on one of its scale-pans, and known masses on the other, the latter being varied until a balance is obtained. The operating principle is in reality the balancing of two forces, the earth's attraction for the mass on one pan being just counteracted by the earth's attraction for the known masses on the other.

The mass of a substance per unit volume is known as its density, a dense substance being one in which a large quantity of matter occupies a small volume. A gallon of water is found to have a mass of 8.34 lb., and since its volume is 231 cu. in. = 0.1337 cu.ft., the density of water is 8.34 lb./0.1337 cu.ft. = 62.4 lb. per cu.ft. In metric units, it is 1 gm. per cu. cm.

Measurement of Time
The regularity of the earth's motion around the sun affords the basis for measurements of time. The earth revolves around the sun once a year (about 365 1/4 days). Its orbit or ecliptic is strictly an ellipse with the sun at one focus, but it may be considered approximately like a circle having a radius of 92,900,000 mi. The speed of the earth along this path varies slightly on account of the eccentricity of the orbit, the speed being greater where the earth is nearer the sun. The earth also rotates uniformly on its axis once a day. The axis passes through the north and south geographic poles, and is not perpendicular to the plane of the ecliptic but is inclined about 23.5o from a perpendicular position. The direction of the axis remains almost fixed in space as the earth rotates, and points almost directly toward the North Star, Polaris.

The stars are tremendously distant, the nearest star being many thousand times as far away as the sun. For this reason, the stars appear almost like fixed points in space, occupying virtually the same positions regardless of the position of the earth in its orbit. To us, it appears that the earth is stationary and that the sun and stars move. When one of the celestial bodies appears to pass through the plane of a given meridian it is said to cross the meridian.

If the instance that a given star crosses the meridian is recorded on two successive nights, the elapsed interval will be the time required for one complete rotation of the earth with reference to a star. This is called a sidereal day, and this constant interval is used in astronomical measurements. On the other hand, if the instance that the suncrosses the meridian are recorded on two successive days, the elapsed interval will be the time required for an apparent rotation of the earth with respect to the sun, and this is called a solar day. The solar days vary somewhat in length, the average throughout the year is known as the mean solar day. Through the course of a year, a given point on the earth is facing the sun 365 times must face a fixed point in space (i.e., a star) 366 times, and owing to this fact the mean solar day is about 366/365 of a sidereal day; that is, the mean solar day is about 4 min. longer than the sidereal day.

The mean solar day is subdivided into 24 hours, each hour being further divided into 60 minutes, and each minute into 60 seconds. Thus the mean solar day is composed of 86,400 mean solar seconds. This means solar second is the unit of time that is in general use for physical and engineering work, as well as for everyday purposes.

In spring-driven clocks or watches a gear train is allowed to run down at a slow and uniform rate under the action of an escapement, controlled either by a pendulum or a balance wheel, and the gear train turns the hands of the instrument in front of a dial or faceplate. In the synchronous electric clock, the hands are driven by a small motor that is connected to an alternating-current circuit and runs in synchronize with the generators at the power station, their speed is accurately controlled.

For the recording of official time, a precision clock is used, the accuracy of which is checked at regular intervals with a meridian telescope. Precision clocks are designed and constructed with the utmost care and are kept in constant-temperature rooms to insure uniform operation. The mechanism is enclosed in a glass case from which most of the air is removed. They are the most accurate timekeepers available.

In scientific and engineering work, it is usually desired to measure the duration of an interval of time rather than to determine the correct time at a certain instant. For this purpose, the familiar stopwatch is widely used. In laboratory work, clocks are used in which each sweep of the pendulum operates an electrical contact in a sounder circuit, the audible clicks of the sounder making the intervals easy to count. Short time intervals can be measured accurately by indirect methods that make use of tuning forks, chronographs, oscillographs, and crystals exhibiting the piezoelectric effect.

Using basic arithmetic and two simple equations anyone can become an astronomical genius.

Most people don’t realize how easy it is to calculate the paths of natural and man-made satellites. Rather than just Google these facts, it is far more satisfying to work them out for ourselves. Doing so will also help us to understand how gravity works, and how it keeps objects in orbit, as our planet around the Sun.

Two Equations and One Force
First, we need to understand the equation that determines the gravitational force between two objects. The larger object is usually called M because it has more mass, the smaller object is called m. The radius of the circle describing the orbit, which is also the distance between the centers of the two objects is called r. G is a constant or a number that is always of the same value when using metric unit measurements. Its purpose is to balance both sides of the equation.

This is the equation for the gravitational force or F:

F = GMm/r²

We only have to multiply G, M, and m together and then divide by r².

But there is another equation that describes the force acting towards the center of the circle that an object is circling. This is perfect for us because it describes well the gravitational force that pulls on an object in orbit.

Our second equation is F = mv²/r.

All the symbols are the same as in the first equation but now we also have the velocity of the orbiting object (v). We may intuitively understand this equation. If we have ever swung a ball on a rope around in a circle, we know that the faster it goes, the more force we have to exert on it to keep it from flying off. As the force in both equations is the same force, we can write:

mv²/r = GMm/r²

Simplifying Even Further Mbr>It’s getting even easier because after the cancellations (m/r is duplicated on both sides of the equation) we get:

v² = GM/r

Let’s use this simple equation to find Earth’s velocity or speed around the Sun.

v = vGM/r

Now, all we need to do is plug the numbers into this equation. The numbers are large, and some find them daunting. But even scientists and mathematicians are scared of big numbers, so they use a trick to cut them down to size. For example, instead of writing 1,000,000,000,000, they write 10¹², and this style of notation will make things a lot easier for us.

Crunching the Numbers

G = 6.672 x 10 ? ¹¹ (10 ? ¹¹ is the same as 1 divided by 10 ¹¹ )

The Sun’s mass, M = 1.989 x 10 ³º kilograms (now that is a big number)

Earth’s distance from the center of the Sun (average) = 1.496 x 10 ¹¹ meters.

V = v (6.672 x 10 ? ¹¹ x 1.989 x 10 ³º x (1/1.496) x 10 ? ¹¹)

V = 29,780 meters per second or 29.78 kilometers per second or 18.61 miles per second or 66,996 miles per hour.

A Greater Perspective
When we work out orbits for ourselves, it impresses upon us the orders of magnitude involved in our universe; imagine, the Earth is moving around the Sun at about 87 times the speed of sound! If we can become comfortable in our arithmetic using powers of ten, then the results can be truly astronomical.

Lesson Review

Directions: Follow the instructions in each Part below to complete the assignment. Remember to cite your resources. Citation examples are provided below the Review.

Part A

Directions: Answer each of the following questions.

1. The Mars Climate Orbiter crash was explained as being caused by a mix-up between metric and imperial units. The computer was programmed to work with pound weight (lbF) instead of newton. Given that the weight of 1 kg is equivalent to the weight of 2.2 pounds (lb), or 2.2 lbF, and that the weight of 1 kg (or 2.2 lbF) is 9.8 N:

a. Find the force in newtons of the weight of 1.0 lbF.
b. If the thrusters to put the craft into orbit were meant to use a value in N but used the same value in lb F, would they slow the craft more or less?
c. Analysis of the mission failure showed the thrusters force was 4.45 times too large, is the failure correctly explained by a unit mix-up?

2. Usain Bolt holds the world record for the 100 m sprint with a time of 9.58 s. His top speed is about 43.45 kmh-1.

a. What is Usain's average speed in...ms-1...kmh-1?
b. Why was his average speed less than his top speed?
c. How long would the race take if Usain had run at his top speed for the entire race?

3. It takes 40 N for Tamara to push a chair slowly and steadily across the carpet. She pushes the chair 4 m from one side of the room to the other.

a. How much work did Tamara do?
b. What happened to the work she did?
c. How could Tamar reduce the amount of work she is doing?

Part B

Directions: Answer each of the following questions.

1. Which of the following is true?

a. The earth revolves around the sun once a year.

b. The earth revolves around the sun for about 365 1/4 days.

c. Earth's orbit or ecliptic is strictly an ellipse with the sun at one focus.

d. The speed of the earth varies slightly on account of the eccentricity of the orbit.

e. All of these

2. The mean solar day is about __________ than the sidereal day.

3. Short time intervals can be measured accurately by indirect methods that make use of tuning __________.

4. The world land speed record is 763.0 mi/h, set on October 15, 1997, by Andy Green in the jet-engine car Thrust SS C. Express this speed in meters per second.

5. What is the quantity which Physics deals?

6. The accuracy of a precision clock is checked at regular intervals with _______________.

7. 1 meter = ________ in.

8. 1 yard = __________ meter.

9. What is used for the record of official time?

10. Any particular object is composed of a definite quantity of matter determined by _______________.

11. What is the basis for measurements of time-based on?

12. The tallest tree in the United States is Founder's Tree, a redwood in northern California. Its height is 364 ft. and its girth is 47.1 ft. Express these dimensions in meters.

13. 1 kilometer = _________ mile.

14. In scientific and engineering work, it is usually desired to measure the duration of an interval of time rather than to determine the correct time at a certain instant. What is it?

15. Which of the following is false about the precision clock?

a. Its accuracy is checked at regular intervals with a meridian telescope.

b. They are the least accurate timekeepers available.

c. Precision clocks are designed and constructed with the utmost care.

d. Precision clocks are kept in constant-temperature rooms to insure uniform operation.

e. It is used to record the official time.

x

Let the rubric below guide your writing:

Rubric

• All responses must include complete sentences with supporting information from the lesson
• each response includes cited resources
• points are deducted if no resources are cited

Define ohm's law?

Understanding Ohm's Law Fundamentals

Electric circuits are all about voltage, current, and resistance. These three quantities are related to each other through Ohm's law, which is fundamental to the study of electric circuits.

Relationship Between Voltage, Current, and Resistance

Voltage, measured in volts (V), is the electric pressure that causes current to flow. Current, measured in amperes (A), is the rate of flow of electric charge. Resistance, measured in ohms (Ω), is the opposition to the flow of current.

Ohm's law relates voltage, current, and resistance as follows:

V = I × R

where V is the voltage, I is the current, and R is the resistance.

Ohm's Triangle and Formula Derivation

Ohm's triangle is a useful tool for remembering and applying Ohm's law. It is a triangle with voltage, current, and resistance along the three sides. The formula for each quantity can be derived by covering the side corresponding to that quantity and multiplying the other two quantities.

For example, to find the voltage, cover the voltage side and multiply the current and resistance. To find the current, cover the current side and multiply the voltage and resistance. Similarly, to find the resistance, cover the resistance side and multiply the voltage and current.

Direct and Inverse Proportionality in Circuits

Current and voltage are directly proportional to each other, meaning that if voltage is increased, current will also increase. Similarly, if voltage is decreased, current will also decrease.

Resistance and current are inversely proportional to each other, meaning that if resistance is increased, current will decrease and vice versa.

Electron Flow and Resistance in Circuits

Ohm's law assumes that electrons flow through the circuit in a continuous and smooth manner. However, this is not always the case. The flow of electrons is affected by the resistance provided by the components in the circuit.

The resistance of a conductor is affected by its length, cross-sectional area, and temperature. Longer conductors with smaller cross-sectional areas and higher temperatures have higher resistance.

Importance of Resistance in Circuit Protection

Resistance plays a vital role in protecting electric circuits from damage caused by excessive current. The resistance provided by fuses and circuit breakers is used to limit the current and protect the circuit.

Applying Ohm's Law to Practical Problems

Ohm's law can be applied to solve practical problems related to electric circuits. For example, it can be used to calculate the voltage, current, or resistance in a circuit, or to determine the power consumed by a circuit.

When applying Ohm's law, remember to use the Ohm's triangle to derive the formula for each quantity, and consider the direct and inverse proportionality between voltage, current, and resistance

PLEASE HELP ASAP PLEASE

Physics As A Discipline

Objectives:

• Students will understand the properties of matter and energy and the interactions between them.

• describe energy/matter and their various forms and relationships

• describe interactions of two or more things and the effect each has on the other

• understand cause and effect relationships that allow predictions to be made

Directions: Read the lesson and complete the Practice Activities, but submit only the Review questions for grading.

Introduction

Physics is a huge subject, and in this lesson, you are going to consider how physics is relevant to everyday life.

Have you ever stopped to think why this fabulous subject is different from the other sciences? As it is also a science, how is it similar? In what ways is a crystal-growing in a beaker in Chemistry, a flower in the field in Biology and Physics, and gravity all considered to be science? Who are some of the famous physicists and what are their contributions to the modern world?

Today's lesson will let you explore these ideas in much greater depth, and open up your mind as to what careers you could follow if you wish to be involved with physics.

Vocabulary

• physics

• physicist

• mechanics

• thermodynamics

• vibrations

• optics

• matter

• gravitation

What is physics?

It is defined as a science that deals with matter and energy and their interactions. It is also important for physics are the mathematical calculations designed to create realism that mimics the real world in graphically-intensive applications like PC games, animation, and simulation such as car crashes. and can be summarized as the study of how objects (from the very tiny to the very big) behave.

It has many branches and these are constantly growing as new and different exciting discoveries are made. Today you will briefly review the main branches.

By the end of the nineteenth century, after more than two thousand years of intellectual struggle that began with the Greek philosophers, physical scientists had reason to believe that they were beginning to understand the universe. Their theories of matter and energy, of electricity and magnetism, of heat and sound and light were confirmed in laboratories throughout the world with increasing precision. Experimentation was the method, and mathematics the language, of a powerful, coherent body of knowledge called classical physics.

Physics couldn't exist without physicists who discover the laws that govern our universe. Here you will learn about some of the most famous physicists, and their contribution to this subject.

Great Physicists

Sir Isaac Newton (1642-1727), an English physicist and mathematician, is considered by many to be the greatest physicist of all time. His most famous contributions to physics are his law of gravitation and laws of motion. He also invented calculus and made important discoveries in the field of optics. For example, the discovery that white light may be split into the colors of the rainbow by a prism. The SI unit of force is named after him.

Andre-Marie Ampere (1775-1836), a French physicist is most famous for investigating the magnetic fields produced by current-carrying wires. His work extended that of the Danish physicist Hans Oersted, who discovered in 1819 that a compass needle was deflected by a current-carrying wire. He also invented the solenoid. Today, the law that governs the magnetic fields produced by electric currents is called Ampere's Law, and the SI unit of electric current is named in his honor.

Carl Friederich Gauss (1777-1855), a German mathematician is most famous for his discoveries in pure mathematics. Indeed, he has been dubbed the 'prince of mathematics'. However, he also made a number of important contributions to physics. He invented the magnetometer and with the German physicist Wilhelm Weber measured the intensity of magnetic forces. He also took Coulomb's famous inverse-square law for the electric field of a point charge and generalized it to an arbitrary charged distribution. This more general law is now known as Gauss's Law.

Michael Faraday (1791-1867), an English physicist was one of the greatest experimentalists in the history of physics. This is remarkable as he had no formal training. Instead he learned about physics and chemistry by working as an assistant to Sir Humphrey Davy. Faraday made many important contributions to the study of electricity and magnetism, including the discovery of electromagnetic induction (now known as Faraday's Law), the invention of the electric motor, and the laws of electrolysis. The SI unit of capacitance is named after him.

William Thomson, Lord Kelvin (1824-1907), the British physicist who published many important papers on the conservation and dissipation of energy. Kelvin also made contributions to other branches of physics (such as fluid mechanics), and was in charge of laying the first successful transatlantic cable in 1866. The SI unit of absolute temperature is named after him.

Albert Einstein (1879-1955). In 1905, Einstein published a paper on what he called the Special Theory of Relativity, which correctly describes the motion of particles traveling at speeds close to the speed of light. The theory is based upon the simple postulates that the laws of physics are the same for all inertial (i.e. non-accelerating) observers and that the speed of light is the same for all inertial observers (regardless of their motion relative to the source of the light). This theory includes the famous formula E = mc2. He subsequently developed the General Theory of Relativity, which is effectively a theory of gravitation. Einstein also contributed to the development of quantum theory. In 1905 he published a paper explaining the photoelectric effect, by postulating that light consists of particles (now known as photons). For this work, Einstein received the 1921 Nobel Prize for Physics.

In 1897 the physicist Joseph John Thomson (1856-1940) discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube, an area being investigated by numerous scientists at the time. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of "bodies much smaller than atoms" that he calculated as having a very large value for the charge to mass ratio. Later he estimated the value of the charge itself. In 1904 he suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces. His efforts to estimate the number of electrons in an atom from measurements of the scattering of light, X, beta, and gamma rays initiated the research trajectory along which his student Ernest Rutherford moved. Thomson's last important experimental program focused on determining the nature of positively charged particles. Here his techniques led to the development of the mass spectroscope, an instrument perfected by his assistant, Francis Aston, for which Aston received the Nobel Prize in 1922.

Johannes Diderik van der Waals (1837-1923) was a Dutch scientist famous "for his work on the equation of state for gases and liquids", for which he won the Nobel Prize in physics in 1910. Van der Waals was the first to realize the necessity of taking into account the volumes of molecules and the intermolecular forces (now generally called "van der Waals forces") in establishing the relationship between the pressure, volume, and temperature of gases and liquids.

Marie Sklodowska Curie (1867-1934) was the first person ever to receive two Nobel prizes: the first in 1903 in physics, shared with her husband Pierre and Henri Becquerel for the discovery of the phenomenon of radioactivity; and the second in 1911 in chemistry for the discovery of the radioactive elements polonium and radium.

Sir William Ramsayand Lord Rayleigh (born John William Strutt) published their discovery of argon in 1895: "Argon, a New Constituent of the Atmosphere". Rayleigh was led into the investigation by small anomalies he found in measurements of the density of nitrogen purified by different methods. Those different methods led to different quantities of nitrogen, and thus to different proportions of nitrogen and a hitherto unsuspected atmospheric gas. Argon was the first noble gas isolated. Naturally, there was no place for it in the periodic table as it then existed. Ramsay's subsequent work isolated helium and discovered neon, krypton, and xenon by the end of the century. Ramsay and Rayleigh were awarded Nobel Prizes in 1904. Note the plural "Prizes": Rayleigh was awarded the physics prize for argon, while Ramsay was awarded the chemistry prize for Argon and the family of noble gases.

Physics as a Career

Physics is all around you, and thanks to the advances in physics over the last 2000 years, there is now a great deal about the world around you that can be explained in terms of science alone. Here are some of the many branches of physics you could have a career in!

Astronomy: Study of Astral bodies
Atomic Physics: Study of forces and particles at the atomic level
Cosmology: How the physical universe formed.
Dynamics: Effects on physical by external forces.
Electricity: Study of electrical charges and the forces they create.
Electrodynamics: Interaction between electrical, magnetic, and mechanical phenomena.
Field Theory: Theoretical study of quantum fields
Fluid Mechanics: The study of materials in a field state.
High Energy Physics (also known as Particle Physics): The interaction of elementary particles.
Hydrostatics / Hydrodynamics: The study of solid bodies in relatively moving water or in equilibrium to it.
Magnetism: The study of magnets and their fields.
Mechanics: Effects of external forces on objects in terms of space.
Nuclear Physics: The study of the atomic nuclei and their decay.
Optics: The study of light and vision.
Particle Physics (also known as High Energy Physics): The study of elementary particles.
Plasma Physics: The study of materials in the plasma phase.
Quantum Electrodynamics (also known as Quantum Theory of Light or Quantum Theory of Radiation): A quantum theory of electromagnetic radiation.
Quantum Mechanics: A theory of matter based on the idea that material particles may be described as waves, and waves may be described as particles.
Solid State Physics: The study of materials in the solid phase.
Statics: The study of the equilibrium of external forces acting on material objects.
Surface Physics: The study of solid, liquid, or gas surfaces.
Thermodynamics: The study of mechanical properties of matter related to heat energy.

Comparing the definitions of the sciences

Physics: Study of matter and energy and their relationships.

Chemistry: The science of matter; the branch of the natural sciences dealing with the composition of substances and their properties and reactions.

Biology: The science that studies living organisms.

As you can see there are some similarities between them and some differences. It is helpful if you stop and think of these differences and similarities and write them down to consolidate your understanding.

Now you are going to consider the different parts of physics as part of an exercise, from where Star Trek comes in, to how many different objects around you are linked to physicists

There is a great deal to research and see when it comes to physics.

Practice Activity A: Brainstorm what you already know

Directions: Brainstorm a list of physics concepts, discoveries, or physicists and create a timeline.

Practice Activity B: Using online resources

Directions: Use internet resources to complete the following:

1. Contact a science council to find out about current careers in science. Find out what was in going on in your own state or part of the world.
2. Research what is being currently researched in physics.
3. Physics was used to build the first atomic bomb. Look at the resources to learn the social implications of this decision.
4. Star Trek uses a great deal of physics in the TV programs. Look at the resource on this to learn more. Also, next time you watch Star Trek and see big explosions with sound, remember in space sound does not travel, so it is a bending of physics as well as true physics.
5. Research the forces which drive the need to research physics such as the military aspects and the models of light.

Practice Activity C: How would you define the subject of physics?

Directions: Try and find out as much as you can to define why physics is a discipline. Are there any areas of physics that are more cross-subject than others? Which is more important do you think, a clear understanding of physics or mathematics, or are they equally important?

Practice Activity D: Who is famous on this subject and why?

Directions: Research the men and women (though it appears far fewer women as science once was considered a male career, which of course now it is not!). Who achieved great things in physics. You will be amazed to discover how many objects you use today were created by them.

Practice Activity E: Interview

Directions: Design a "Mock Interview" with a famous Physicist (alive or dead), asking key questions about his/her experiments and breakthrough findings in his/her field of study.

After the interview has been completed, you will create a brochure with information about your physicist. Below is a list of information you should include in the brochure:

• educational background

• previous job experience

• special interests, hobbies

• contributions to the scientific world

• organization memberships

• special honors awarded

Lesson Review

Directions: Follow the instructions in each Part below to complete the assignment. Remember to cite your resources. Citation examples are provided below the Review.

Part A

Directions: Summarize at least one of the Practice Activities. Discuss your findings and be sure to cite any resources that you used in your research.

Part B

Directions: Answer each of the following questions.

1. Marie (Sklodowska) Curie discovered ____________.
2. The study of mechanical properties of matter related to heat energy' defines _________________.
3. A theory of matter based on the idea that material particles may be described as waves and waves may be described as particles._________________

4. The study of mechanical properties of matter related to heat energy. _________________.
5. Study of matter and energy and their relationships. _______
6. This theory describes the motion of particles traveling at speeds close to the speed of light. _________________.

7. The study of the properties of atomic nuclei the forces responsible for the stability or the disintegration of atomic nuclei.

8. What is Sir Isaac Newton famous for?

9. Albert Einstein is famous for __________________.

10. What did Joseph John Thomson discover? _____________.

a farmer wants to know the length of his plots of land in meter but he has only a long rope a 50cm ruler and a 6m long stick. How can he easily measure the length of his plot?

What is the most common cause of gastroenteritis?

Compton effect introduction 

What is the relation of physics with technology?

What are the types of equilibrium?

Define stability?

Define equilibrium?in physics 

Define torque?

What are ?physical quarantities