AP Physics 1 : Work, Energy, and Power

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #81 : Work, Energy, And Power

What is the mass of a bowling ball that maintains an average kinetic energy of  while traveling at ?

Possible Answers:

Correct answer:

Explanation:

For this question we will use the kinetic energy equation.

Plug in and solve for the mass of the bowling ball.

The mass of the bowling ball is .

Example Question #81 : Work, Energy, And Power

A child weighing in an  is walking at . What is his or her average kinetic energy?

Possible Answers:

Correct answer:

Explanation:

For this question use the equation for kinetic energy.

Plug in and solve for the the kinetic energy.

The child will have a kinetic energy equal to .

Example Question #33 : Kinetic Energy

A box of mass  is initially at rest, and is then subject to  of a directing horizontal pulling force. Neglecting friction and air resistance, what is the kinetic energy of the box after ?

Possible Answers:

 

Correct answer:

 

Explanation:

First, solve for the acceleration of the box using Newton's second law.

Plug in and solve for the acceleration.

Now use a kinematic equation to solve for the final velocity.

Plug in and solve for the final velocity.

Finally, we will use the kinetic energy equation to determine the kinetic energy of the box after .

Plug in and solve for the kinetic energy.

The final kinetic energy of the box will be .

Example Question #34 : Kinetic Energy

Two space ships are racing deep in space. At , Spaceship A is at the origin while traveling at . It is coasting, with it’s rockets off. Spaceship B is at . It’s traveling at . It’s rockets are firing with a constant force of . Both rockets have a mass of .

What is the total kinetic energy of the two spaceships at ?

Possible Answers:

None of these

Correct answer:

Explanation:

Finding net velocity of Spaceship :

Finding net velocity of Spaceship :

Example Question #35 : Kinetic Energy

Moment of inertia of disk:

A car with wheels of mass and wheels of radius is traveling at . Treating the wheels as disks of uniform mass density, calculate the rotational kinetic energy of one wheel.

Possible Answers:

None of these

Correct answer:

Explanation:

Finding angular velocity:

Using

and

Combining equations and plugging in values:

Example Question #82 : Work, Energy, And Power

A soccer ball at rest of mass  is accelerated at for . What is the final kinetic energy in Joules of the ball after ?

Possible Answers:

None of these

Correct answer:

Explanation:

First find the final speed of the ball using . Then, use  to find the kinetic energy after 9s.

Example Question #37 : Kinetic Energy

A  missile has a net propulsion force of . Over a brief period, the missile speeds up uniformly from an initial velocity  to . Assume that the missile will not lose mass during fuel consumption and so the net propulsion remains constant. What is the net work done on the rocket in kilojoules?

Possible Answers:

Correct answer:

Explanation:

Find the KE of the missile at each velocity. The difference or change in KE is the net work done on the missile.

Divide by 1000 to convert to

Example Question #81 : Work, Energy, And Power

A bullet with mass  hits the bullseye at . Assuming no loss of energy due to heat or frictional forces, how much energy in Joules did the bullet transfer to the target?

Possible Answers:

Correct answer:

Explanation:

Find the kinetic energy:

Example Question #39 : Kinetic Energy

A sledder of mass  is traveling down a hill with slope of  above the horizontal. If the sledder starts from rest and has an average frictional force of , what is the velocity of the sledder after traveling  along the slope?

Possible Answers:

Correct answer:

Explanation:

We can begin with the expression for conservation of energy for this problem:

We are told that the sledder begins from rest, so we can eliminate initial kinetic energy. Also, if we say that the final height of the sledder is 0, we can eliminate final potential energy. Also, the only work being done is from friction, and the work is being removed from the system, so it will be negative. Therefore, we get:

Substituting in expressions for each of these, we get:

Rearranging for final velocity:

Now we just need an expression for initial height:

Plugging this in, we get:

We have all of these values, so time to plug and chug:

Example Question #40 : Kinetic Energy

Rollercoaster 2

The following train car has just went around the loop of this roller coaster and is now travelling to the left. The train car weighs  and is travelling at a speed of .

What is the approximate kinetic energy of the train car?

Possible Answers:

Correct answer:

Explanation:

Kinetic energy is defined by the following equation:

where  is mass, and  is velocity. 

In this question, you are given the mass and velocity, so by plugging in the given values it is possible to find the kinetic energy (in Joules).

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