# 4.4 Multiple Choice

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## Multiple Choice Practice for Systems of Particles and Linear Momentum

Welcome to Unit 4 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 4 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 4.

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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 ball of mass m strikes a vertical wall with a velocity vi and rebounds with a speed of vf. What is an expression for the magnitude of the impulse exerted on the ball by the floor?
A. mvf
B. m(vf-vi)
C. m(vi-vf)
D. m(vf + vi)

2. A billiards ball (m = 0.16kg) moves with an initial velocity of +2 m/s and collides with an identical billiards ball initially at rest. After the elastic collision, one ball travels with a speed of +0.5 m/s. What is the speed of the other ball?
A. The speed of the other ball is -3 m/s.
B. The speed of the other ball is -1.5 m/s.
C. The speed of the other ball is +1.5 m/s.
D. The speed of the other ball is +3 m/s.

3. A 60kg person and a 75kg person sit on opposite sides of a 4 meter long seesaw. Where is their center of mass?
A. 1.6 meters

4. The blue line on the graph shows the applied force on a 15.0kg shopping cart as a shopper moves down an aisle in the grocery store. Assuming the cart starts at rest, determine the speed of the cart after 3 seconds.
A. 5 m/s
B. 10 m/s
C. 50 m/s
D. 75 m/s

5. A convertible moving with constant velocity on the open highway gets stuck in a snowstorm. Which of the following statements are true?
A. As the snow accumulates in the car, the speed of the car will increase because of conservation of energy.
B. As the snow accumulates in the car, the speed of the car will increase because of conservation of momentum.
C. As the snow accumulates in the car, the speed of the car will decrease because of conservation of energy.

6. How does an airbag work to protect a passenger in a car crash?
A. It increases the momentum change of the passenger.
B. It decreases the momentum change of the passenger.
C. It lengthens the stopping time of the passenger, which reduces the force applied during the crash.

7. Two hockey mascots (named Gritty and Tommy Hawk) are standing at rest in the center of an ice rink. They push apart in opposite directions. The velocity of Gritty is 3 m/s, and the velocity of Tommy Hawk is - 6m/s. Which statement about the masses of the respective mascots is true?
A. Gritty is twice as massive at Tommy Hawk.
B. Tommy Hawk is twice as massive as Gritty.
C. Gritty is three times as massive as Tommy Hawk.

8. Two objects of masses M and 4M are traveling at the same speed v towards each other, with the 4M mass traveling in the negative direction. They collide and stick together. How much kinetic energy is lost in the collision?
A. 0.6mv^2
B. 0.9mv^2
C. 1.6mv^2

9. Three 5kg masses are on a 100 cm board. The board is suspended by a rope attached at the 50cm mark. If mass 1 is at 0cm and mass 2 is at 80cm, where must mass 3 be placed in order to keep the board level?
A. At the 20cm mark
B. At the 50cm mark
C. At the 70cm mark

10. Two carts move towards each other and collide elastically. Cart 1 has a mass of 8kg and moves to the right with a speed of v = 5 m/s. Cart 2 has a mass of 25kg and moves to the left with a speed of v = 1 m/s. After the collision, Cart 1 moves to the left with a speed of 2 m/s. What direction does Cart 2 move after the collision?
A. Cart 2 moves right after the collision
B. Cart 2 moves left after the collision
C. Cart 2 is not moving after the collision

11. A firework explodes into three equally massive pieces, each with their momentum represented by the expression mv. The momentum vectors of two out of the three firework pieces are drawn in the image. What direction does the momentum vector of the third piece point?
A. The third vector must point towards zero degrees.
B. The third vector must point towards 90 degrees.
C. The third vector must point towards 180 degrees

12. Two bocce balls make a partial collision during a game. In this case, which of the following is true about the momentum and kinetic energy?
A. Both momentum and kinetic energy are always conserved.
B. Kinetic energy is always conserved, and momentum may be conserved.
C. Momentum is always conserved, and kinetic energy is never conserved.

13. A rod with uniform density has a length of L and a mass of M. Which of the following is an expression for the rod's center of mass?
A. L/2
B. L/3
C. L/4

14. A 0.15kg baseball is thrown by a catcher and leaves the catcher's hand with a speed of 35 m/s. What is the magnitude of the impulse on the ball?
A. 5.25 Ns
B. 92 Ns
C. 233 Ns

15. A force acting on an object is represented by the expression F(t) = 4t^2. If the object starts at rest, what is the momentum of the object after 5 seconds?
A. 1.1 kg m/s
B. 100 kg m/s
C. 167 kg m/s

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