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AP Physics C: Mech

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Unit 3

3.6 Multiple Choice

5 min read•december 30, 2021

AP Physics C: Mechanics ⚙️

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Multiple Choice Practice for Work, Energy, and Power

Welcome to Unit 3 AP Physics C: Mechanics Multiple Choice Questions! Grab some paper and a pencil 📄 to record your answers as you go. You can see how you did on the Unit 3 Practice Questions Answers and Review sheet once you're done. Don't worry, we have tons of resources available if you get stumped 😕 on a question. And if solo study is not your thing, join a group in Hours! Not ready to take a quiz yet? Take a look at the Intro to Unit 3.

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Facts about the test: The AP Physics C: Mechanics exam has 35 multiple choice questions and you will be given 45 minutes to complete the section. That means it should take you around 15 minutes to complete 12 questions.

The following questions were not written by College Board and, although they cover information outlined in the AP Physics C: Mechanics Course and Exam Description, the formatting on the exam may be different.

1. A 0.5kg object moves along a path according to the potential energy function U(x) = 0.25x^3, where U is in Joules and x is in meters. If the total energy of the particle is 14 J, find its speed at x = 2m.

A. 2.0 m/s

B. 6.9 m/s

C. 12 m/s

D. 48 m/s

2. A feather and a bowling ball are dropped from the top of a cliff. Assuming no air resistance, which of the following statements are true?

A. The bowling ball will reach the ground before the feather.

B. When they reach the ground, the bowling ball is going faster than the feather.

C. When they reach the ground, the bowling ball has more kinetic energy than the feather.

D. Just as they were released, both objects had the same about of gravitational potential energy.

3. An object’s potential energy function is given by U(x) = 7x^2 + 4. Which of the following is an expression for the force on the particle?

A. F(x) = -(7/3)x^3 + 2x

B. F(x) = -14x

C. F(x) = (7/3)x^3 + 2x

D. F(x) = 14x

4. A librarian pushes a 100kg cart of books up a ramp at a constant speed of 1.5 m/s. It takes him 5 seconds to get to the top of the ramp, which has a height of 6.5 meters. With how much force is he pushing?

A. 850 N

B. 1275 N

C. 1911 N

5. Two identical rocks are launched vertically upward with a slingshot. If Rock A is launched with twice the speed as Rock B, which of the following statements are true? Assume negligible air resistance.

A. The maximum height of Rock A will be equal to the maximum height of Rock B.

B. The maximum height of Rock A will be twice as large as the maximum height of Rock B.

C. The maximum height of Rock A will be four times as large as the maximum height of Rock B.

6. A cart sits at rest at the top of a hill with a height of 25 meters. Assuming no friction, how fast is it going when it gets to the bottom of the hill?

A. 22 m/s

B. 25 m/s

C. 490 m/s

D. Impossible to know without knowing the mass of the cart.

7. A 1010 kg sports car is moving at a speed of 45 m/s on a straight road. A 1300 kg sedan is moving at a speed of 26 m/s on the same road. Both encounter the same constant braking force and are brought rest. Which car travels a shorter distance before stopping?

A. Impossible to know with the information given.

B. Both travel the same distance

C. The sports car

D. The sedan

8. A crane delivers 200kW of power as it lifts a cargo container 33 meters to the 10th floor of a new building. It takes the crane 15 seconds to lift the container at a constant speed. What is the mass of the cargo container?

A. 90 kg

B. 400 kg

C. 900 kg

D. 9000 kg

9. A 4.0 kg cart sits at rest at the top of a 20 meter frictionless hill. After it rolls down the hill, it encounters a massless, frictionless spring, which it compresses 0.5 meters and comes to rest again. What is the spring constant of the spring?

A. 784 N/m

B. 1568 N/m

C. 3136 N/m

D. 6272 N/m

10. A spring is stretched 4 meters from its equilibrium position by a conservative force F, measured in Newtons. If the expression for the spring force is F(x) = -3x^2, what is the resulting change in potential energy?

A. 6 J

B. 12 J

C. 64 J

D. 192 J

11. A babysitter pulls the handle of a wagon with a force F at an angle theta with the ground. The work done by F as it the wagon moves a distance D across the ground can be expressed using which of the following?

A. FD

B. FDcos(theta)

C. FDsin(theta)

D. FDtan(theta)

12. The potential energy function of a 2.0kg object moving along an x-axis is expressed U(x) = x^2. What is the acceleration of the particle at x = 5.0m?

A. -10 m/s^2

B. -5 m/s^2

C. 12.5 m/s^2

D. 25 m/s^2

13. A arrow is shot straight upward into the air. Compare the work done by gravity as the arrow travels upward versus when it is on the way down.

A. The work done by gravity is positive in both directions.

B. The work done by gravity is positive on the way up and negative on the way down.

C. The work done by gravity is negative on the way up and positive on the way down.

D. The work done by gravity is negative in both directions.

14. Two identical masses start with a speed of 5 m/s and travel up a frictionless ramp until they stop. If Ramp A is tilted at a 30 degree angle, and Ramp B is at a 60 degree angle, which mass is higher from the ground on their respective ramps?

A. The masses travel to the same height above the ground.

B. The mass on Ramp A is higher from the ground.

C. The mass on Ramp B is higher from the ground.

D. There is not enough information to tell.

15. The work done to stretch an ideal spring 20cm away from its equilibrium position is 8 Joules. How much work is required to stretch the spring 60cm?

A. 24 Joules

B. 72 Joules

C. 120 Joules

D. 400 Joules

Time to Check Your Answers on Unit 3 Practice Questions Answers and Review! 🙌

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