CAS PY 105 Chapter Notes - Chapter 7: Net Force

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9 Apr 2015

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Energy is a scalar quantity associated with the state (or condition) of one or more object. Energy is a number that we associate with a system of one or more objects: kinetic energy k is energy associated with the state of motion of an object. The faster the object moves, the greater is its kinetic energy. When the object is stationary, its kinetic energy is zero: for an object of mass m whose speed v is well below the speed of light (e1) Work and kinetic energy: work w is energy transferred to or from an object by means of a force acting on the object. Energy transferred to the object is positive work, and energy transferred from the object is negative work. Work and kinetic energy: to calculate the work a force does on an object as the object moves through some displacement, we use only the force component along the object"s displacement.

Related Questions

Which of the following statement are true mechanical energy? Include all that apply.

1.The total amount of mechanical energy of an object is the sum of its potential energy and the kinetic energy.

2. Heat is a form of mechanical energy.

3. The mechanical energy of an object is always conserved.

4. When non-conservative forces do work, energy is transformed from kinetic to potential (or vice versa), but the total mechanical energy is conserved.

5. A bowling ball is mounted from a ceiling by way of a strong cable. It is a drawback and released, allowed to swing as a pendulum. As it swings from its highest position to its lowest position, the total mechanical energy is mostly conserved.

6. When a friction force does work on an object, the total mechanical energy of that object is changed.

7. The total mechanical energy of an object remains constant if the only forces doing work on the object are conservative forces.

8. If an object gains mechanical energy, then one can be certain that a non-conservative force is doing work.

is defined as $K=(1/2)mv^2$ . It seems reasonable to say that the speed of an object--and, therefore, its kinetic energy--can be changed by performing work on the object. In this problem, we will explore the mathematical relationship between the work done on an object and the change in the kinetic energy of that object.

Let us now consider the situation quantitatively. Let the mass of the sled be and the magnitude of the net force acting on the sled be. The sled starts from rest.

Consider an interval of time during which the sled covers a distance

and the speed of the sled increases from

. We will use this information to find the relationship between the work done by the net force (otherwise known as the network) and the change in the kinetic energy of the sled.

Find the net force

acting on the sled.

Express your answer in terms of someor all of the variables

, and

Find the net work

done on the sled.

Express your answer in terms of someor all of the variables

is defined as $K=(1/2)mv^2$ . It seems reasonable to say that the speed of anobject--and, therefore, its kinetic energy--can be changed byperforming work on the object. In this problem, we willexplore the mathematical relationship between the work done on anobject and the change in the kinetic energy of that object.

Let us now consider the situationquantitatively. Let the mass of the sled be and the magnitude of the net force acting on the sled be. The sled starts from rest.

Consider an interval of time duringwhich the sled covers a distance

and the speed of the sled increases from

. We will use this information to find the relationshipbetween the work done by the net force (otherwise known as thenet work) and the change in the kinetic energy of thesled.

Find the net force

acting on the sled.

Express your answer in terms of someor all of the variables

, and

Find the net work

done on the sled.

Express your answer in terms of someor all of the variables

and

graywildebeest386

A 48.1-kg athlete leaps straight up into the air from a trampolinewith an initial speed of 9.6 m/s. The goal of this problem is tofind the maximum height she attains and her speed at half maximumheight.
(a) What are the interacting objects and how do theyinteract?

(b) Select the height at which the athlete's speed is 9.6 m/s as y= 0. What is her kinetic energy at this point? What is thegravitational potential energy associated with the athlete?
kinetic energy J
potential energy J

(c) What is her kinetic energy at maximum height? What is thegravitational potential energy associated with the athlete?
kinetic energy J
potential energy J

(d) Write a general equation for energy conservation in this caseand solve for the maximum height. (Do this on paper. Yourinstructor may ask you to turn in this work.)

(e) Substitute and obtain a numerical answer.
m

(f) Write the general equation for energy conservation and solvefor the velocity at half the maximum height. (Do this on paper.Your instructor may ask you to turn in this work.)

(g) Substitute and obtain a numerical answer.
m/s

CAS PY 105 Chapter Notes - Chapter 7: Net Force

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