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PHY 205 Lecture Notes - Lecture 12: Goods Wagon, Rubber Band

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School
MSU
Department
Physics
Course
PHY 205
Professor
Kuntz

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Document Summary

Freight car a is moving toward identical freight car b that is at rest. When they collide, both freight carts couple together. Compared with the initial speed of freight car a, the speed of the coupled freight cars is ______________ half. Define work defined as the product of force exerted on an object and the distance the objects moves (in the same direction as the force) Is done only when the force succeeds in moving the body it acts upon. If you push against a stationary brick wall for several minutes, you do no work on the wall explanation- you may do work on your muscles, but not on the wall. Work falls into two categories which are work done against another force and work done to change the speed of an object. Work is done in lifting a barbell. how much work is done in lifting a twice as heavy barbell the same distance? twice as much

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

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Related Questions

1. Can work be done on a system if there is no motion?

A) Yes, if an outside force is provided B) Yes, since motion is only relative C) No, since a system which is not moving has no energy D) No, because of the way work is defined 

2. The quantity 1/2 mv 2 is

 A) the power supplied to the object by the force  B) the work done on the object by the force  C) the kinetic energy of the object. D) the potential energy of the object.

3. If you push twice as hard against a stationary brick wall, the amount of work you do 

A) doubles. B) is cut in half  C) remains constant but non-zero  D) remains constant at zero 

4. If the net work done on an object is positive, then the object's kinetic energy 

A) increases. B) decreases  C) remains the same D) is zero

5 A force of 20 N moves an object in the direction of the force. The work done when the object moves from 2.0 to 4.0 m is o A) 20 J OB) 40 J oC) 60 J D) 80 J


1.

While helping a friend move, you push a 11.5 kg dolly with a forceof 11.0 N. Assume there are no other forces acting on the dolly. Ifthe dolly starts at rest, how far does it move in 3.50 s?
1 m

2.

At a lumberjack competition an axe with a mass of 1.25 kg is thrownat a target with a speed of 41 m/s. When it hits the target, itpenetrates to a depth of 0.055 m.
(a) What was the average force exerted by the target on theaxe?
1 N

(b) If the mass of the axe is halved, and the force exerted by thetarget on the axe remains the same, by what multiplicative factordoes the penetration depth change?
2
It doubles. It increases by a factor of the square root of two. Itdoes not change. It decreases by a factor of the square root oftwo. It halves.
Your work in question(s) will also be submitted or saved.
3

Your 1500 kg car pulls a 540 kg trailer away from a stop sign withan acceleration of 2.00 m/s2. (Note the answers should be given inkN.)
(a) What is the net force exerted by the car on the trailer?
1 kN

(b) What force does the trailer exert on the car?
2 kN

(c) What is the net force acting on the car?
3 kN


4.

Two boxes sit next to, and touching, each other on a frictionlesshorizontal surface. The lighter box has a mass of 5.31 kg and theheavier box has a mass of 7.29 kg.
(a) Find the contact force between these boxes when a horizontalforce of 6.1 N is applied to the light one.
1 N

(b) If the 6.1 N force is applied to the heavy box instead, is thecontact force between the boxes the same as, greater than, or lessthan the contact force in part (a)?
2

(c) Verify your answer to part (b) by calculating the contact forcein this case.
3 N

5.

A child sits in a wagon and together they have a mass of 25 kg. Thewagon is pulled with a constant speed by a handle that is at anangle of 22° above the horizontal. If the normal force exerted onthe wagon is 210 N, what is the force F applied to thehandle?
1 N

6.

An object acted on by three forces moves with constant velocity.One force acting on the object is in the positive x direction andhas a magnitude of 6.7 N; a second force has a magnitude of 4.5 Nand points in the negative y direction. Find the direction andmagnitude of the third force acting on the object.
1 N
2° (counterclockwise from the +x axis)


7.

A chain is used to lift a 1200 kg car vertically upward with anacceleration of 0.90 m/s2. What is the tension in the chain?
1 N

8.

A 22.5 kg box (m1) rests on a table.

(a) What is the weight of the box?
1 N
What is the normal force acting on it?
2 N (upward)
(b) A 12.5 kg box (m2) is placed directly on top of the 22.5 kgbox.
Determine the normal force that the table exerts on the 22.5 kgbox.
3 N (upward)
Determine the normal force that the 22.5 kg box exerts on the 12.5kg box.
4 N (upward)

9.

Your friend has a weight of 127 lb when standing on a scale. Youtake the scale to an elevator where you notice your friend's weighton the scale reads 108 lb. What are the direction and magnitude ofthe elevator's acceleration?
Direction 1
Magnitude 2 m/s2

10.

When you lift a package with a force of 82 N, the packageaccelerates upward at a rate of a. If, instead, you lift with aforce of 93 N, the package now has an acceleration of 8 multipliedby a.
(a) Find the weight of the package.
1 N

(b) Find the acceleration a.
2 m/s2

11.

One 3.1 kg paint bucket is hanging by a massless cord from another3.1 kg paint bucket, also hanging by a massless cord, as shownbelow.

(a) If the buckets are at rest, what is the tension in eachcord?
(lower cord) 1 N
(upper cord) 2 N

(b) If the two buckets are pulled upward with an acceleration of1.30 m/s2 by the upper cord, calculate the tension in eachcord.
(lower cord) 3 N
(upper cord)5

12)
Your friend has a pair of fuzzy dice with a mass of 1.32 g hangingfrom his rear-view mirror.
(a) When he accelerates from a stoplight, the dice deflect backwardtoward the rear of the car hanging at an angle of 6.18° relative tothe vertical. Find the tension in the string holding thedice.
N

(b) At what angle to the vertical will the tension in the string betwice the weight of the dice?
°


a.) A hockey puck is observed to be sliding along a flatfrictionless surface at a speed of 4 cm/min. There is no net forceacting on the puck. Assuming it doesn't smash into anything, howfast will the puck be going 17 min later?
cm/min

b.) An object is accelerating. Which one of the followingstatements is true?
The object must be speeding up.
Gravity must be causing the object to accelerate.
The object must be changing directions.
The object must be slowing down.
There is a net force acting on the object.

c.) A 100 kg block weighs 220 lb on Earth. If the block weretransported to a planetary body that had a smaller free fallacceleration (as compared to Earth), which one of the followingwould be true?
The block would have the same weight and a smaller mass.
The block would have the same mass and a bigger weight.
The block would have the same mass and the same weight.
The block would have the same weight and a bigger mass.
The block would have the same mass and a smaller weight.
d.) What does it mean (in physics) to say that a quantity isconserved?
It means that the quantity is not being used.
It means the total amount is zero.
It means the total amount never changes.
It means it's being saved up.

e.) At a certain point in time, the total energy of a closed systemis observed to be 176 J. Which one of the following statements istrue?
Three hours later the energy of the system is 352 J.
Four hours later the energy of the system is 88 J.
All of the energy must be kinetic if the objects are moving.
Twelve hours later the energy of the system is 176 J.
Some of the energy must be potential.

g.) Which of the following statements are impossible? Choose allthat apply.
The parked truck had 8770 J of KE.
The scooter had 0 J of KE and 0 kg·m/s of momentum.
A ball moving in a circle had 0 N of net force acting on it.
A box had an acceleration of 0 m/s2 while a net force of 311 Nacted on it.
Jack exerted 18 N of force due east on a cart. As a direct result,the cart exerted 18 N of force due west upon Jack.
A toothpick exerts a smaller gravitational force upon the Moon thanthe Moon exerts upon it.

a.) Two balls make up a closed system. Ball A has 701 J of energyand ball B has 78 J. After they collide, ball A has 665 J. How muchenergy does ball B have after they collide?
J

b.) An asteroid and a comet collide head on. Prior to thecollision, the asteroid has a momentum of 700,000 kg·m/s up and thecomet has a momentum of 800,000 kg·m/s down. After the collisionthe asteroid has a momentum of 750,000 kg·m/s down. After thecollision, what is the comet's momentum?
kg·m/s
North
South
East
West
Up
Down
Left
Right
No direction because the comet has stopped

c.) How much does a 28 kg object weigh on Moon? Please feel free toreference the Solar System Data table located at the beginning ofUnit II.
______N

d.) A 660 N net force acts on a 42 kg object. Determine theobject's acceleration.
_____m/s2

e.) Calculate the gravitational force between a 657 kg object(resting on Earth) and the Moon. The mass of the Moon is 7.347×1022kg and the distance between the object & the Moon is 3.844×108m.
____N