5.6 MC Answers and Review
8 min readβ’december 20, 2021
AP Physics 1Β π‘
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Answers and Review for Multiple Choice Practice on Momentum
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βSTOP β Before you look at the answers make sure you gave this practice quiz a try so you can assess your understanding of the concepts covered in Unit 5. Click here for the practice questions: AP Physics 1 Unit 5 Multiple Choice Questions.
Facts about the test: The AP Physics 1 exam has 50 multiple choice questions (45 single-select and 5 multiple-select) and you will be given 90 minutes to complete the section. That means it should take you around 15 minutes to complete 8 questions.
The following questions were not written by College Board and, although they cover information outlined in the AP Physics 1 Course and Exam Description, the formatting on the exam may be different.
1. In order to catch a ball, a baseball player naturally moves his or her hand backward in the direction of the ball's motion once the ball contacts the hand. This habit causes the force of impact on the player's hand to be reduced in size principally because ___.
A. the resulting impact velocity is lessened
B. the time of impact is increased
C. the momentum change is decreased
D. the time of impact is decreased
Answer: Remember that the impulse-momentum theorem says that the impulse of an object is either the mass times velocity OR the force times time. Since the impulse value won't change, if we increase the time of impact then the force must decrease.
π Study AP Physics 1, Unit 5.1: Momentum and Impulse
2. Suppose that you're driving down the highway and a grasshopper crashes into the windshield of your car. Which undergoes the greater change is momentum?
A. Grasshopper
B. Car
C. Truck
D. Both the same
Answer: The change in momentum is the same for both due to the difference in mass and the change in velocity for both objects. The car has a huge mass compared to the grasshopper but has a very small change in velocity compared to the grasshopper.
π Study AP Physics 1, Unit 5.2: Representations of Changes in Momentum
3.Β Suppose that you're driving down the highway and a grasshopper crashes into the windshield of your car. Which undergoes the greater force?
A. Grasshopper
B. Car
C. Truck
D. Both the same
Answer: Newton's 3rd Law applies here. The force on the grasshopper and the force on the car are equal and opposite due to Newton's 3rd law. In addition, the impulse is the same since the force and the time are the same for the impact.
π Study AP Physics 1, Unit 5.2: Representations of Changes in Momentum
4. Suppose that you're driving down the highway and a grasshopper crashes into the windshield of your car. Which undergoes the greater acceleration?
A. Grasshopper
B. Car
C. Neither
D. Both the same
Answer: Since the force is the same on each object, using Newton's 2nd law, F = ma, the smaller mass of the grasshopper must have a much higher acceleration! F is the same; m is very small, a is very large!
π Study AP Physics 1, Unit 5.1: Momentum and Impulse
5. An archer shoots an arrow at a pumpkin on a stand. The arrow embeds itself into the pumpkin and both fly off of the stand at the same velocity. Momentum is conserved. What is the relationship between the initial and final kinetic energy for this collision?
A. Ki > Kf
B. Ki < Kf
C. Ki = Kf
D. Cannot be determined without knowing the speed of the two objects after the collision
Answer: This is a perfectly inelastic collision since the two objects stick together. In a perfectly inelastic collision, momentum is conserved but there is a loss of energy and therefore Ki > Kf.
π Study AP Physics 1, Unit 5.4: Conservation of Linear Momentum
6. An archer shoots an arrow at a pumpkin on a stand. The arrow embeds itself into the pumpkin and both fly off of the stand at the same velocity. Momentum is conserved. What type of collision has occurred?
A. Elastic
B. Inelastic
C. Perfectly inelastic
D. Explosion
Answer: This is a perfectly inelastic collision since the two objects stick together. In a perfectly inelastic collision, momentum is conserved but there is a loss of energy and therefore Ki > Kf.
π Study AP Physics 1, Unit 5.4: Conservation of Linear Momentum
7. An archer shoots an arrow at a pumpkin on a stand. The arrow bounces off the pumpkin and both fly off of the stand in different directions. Momentum is conserved and Ki = Kf. What type of collision has occurred?
A. Elastic
B. Inelastic
C. Perfectly inelastic
D. Explosion
Answer: This is an elastic collision since the two objects bounce off each other and both momentum and kinetic energy are conserved.
π Study AP Physics 1, Unit 5.4: Conservation of Linear Momentum
8. An archer shoots an arrow at a pumpkin on a stand. The arrow bounces off the pumpkin and both fly off of the stand-in different directions. Momentum is conserved and Ki > Kf. What type of collision has occurred?
A. Elastic
B. Inelastic
C. Perfectly inelastic
D. Explosion
Answer: This is an inelastic collision since the two objects bounce off each other, momentum is conserved, but kinetic energy is not conserved.
π Study AP Physics 1, Unit 5.4: Conservation of Linear Momentum
9. Cars are equipped with padded dashboards. In collisions, the padded dashboards would be safer than non-padded ones because they ____.
A. Inversely decrease the acceleration divided by time
B. Decrease the impact time
C. Decrease the impulse of the passenger
D. Increase the impact time
Answer: In a car collision, the mass and the change in velocity will not be different whether or not the dashboard is padded. When the dashboard is padded, the time of impact is increased and therefore the impact force must decrease saving the person from serious injury.
π Study AP Physics 1, Unit 5.1: Momentum and Impulse
10. A student conducts an experiment and creates a graph of Force (N) vs. Time (s). How would the student be able to find the impulse of the object from the graph?
A. Find the square root of the y-intercept
B. Find the slope of the best-fit line
C. Find the area of the graph under the curve
D. The impulse cannot be determined from the graph
Answer: Since impulse is Ft, a graph of Force vs. Time will give you impulse if you find the area under the curve. The slope gives you units of N/s (not impulse). The other answers don't make sense.
π Study AP Physics 1, Unit 5.1: Momentum and Impulse
11. A pitcher throws a baseball to the catcher. The catcher catches the ball and brings it to a stop. Ignoring the flight through the air, the baseball encounters two different impulses - the one imparted to it by the pitcher and the one imparted to it by the catcher. How do these two impulses compare?
A. The impulse provided to the ball by the pitcher is equal to that provided by the catcher.
B. The impulse provided to the ball by the pitcher is less than that provided by the catcher.
C. The impulse provided to the ball by the pitcher is greater than that provided by the catcher.
D. It cannot be determined from the information given.
Answer: Impulse is the mass time change in velocity. The baseball mass will not change and the ball should speed up in the pitcher's hand with the same value that the ball slows down when it hits the catcher's mitt (ignoring wind resistance!).
π Study AP Physics 1, Unit 5.3: Open and Closed Systems: Momentum
12. You are sitting at a baseball game when a foul ball comes in your direction. You prepare to catch it bare-handed. To catch it safely, you should _____.
A. move your hands toward the ball during the impact with it
B. move your hands in the same direction as the ball during the impact with it
C. hold your hands as still and steady as possible during the impact with it
D. move out of the way.
Answer: To make sure you feel less force with the same impulse (change in momentum), you need to increase the time of impact. By pulling your hand backward, you effectively increase the time of impact which then decreases the force with the same impulse (change in momentum).
π Study AP Physics 1, Unit 5.3: Open and Closed Systems: Momentum
13. In a collision, an object experiences an impulse. This impulse causes and is equal to the _____________ of the object.
A. force
B. momentum
C. velocity
D. momentum change
Answer: Impulse IS the change in momentum!
π Study AP Physics 1, Unit 5.1: Momentum and Impulse
14. The diagram depicts Before and After velocities of an 800-kg car in two different collisions with a wall. In case A, the car rebounds upon collision. In case B, the car hits the wall, crumples up and stops. Assume that the collision time for each collision is equal. In which case does the car experience the greatest momentum change?
A. Case A
B. Case B
C. Both are the same
D. Not enough information is given
Answer: Be CAREFUL with this one. The car has the SAME mass each time but the change in VELOCITY is much different! For car A, the change in velocity is 9 m/s (since it actually reverses direction) and the change in velocity for car B is only 5 m/s.
π Study AP Physics 1, Unit 5.1: Momentum and Impulse
15. The diagram depicts Before and After velocities of an 800-kg car in two different collisions with a wall. In case A, the car rebounds upon collision. In case B, the car hits the wall, crumples up and stops. Assume that the collision time for each collision is equal. In which case does the car experience the greatest impulse?
A. Case A
B. Case B
C. Both are the same
D. Not enough information is given
Answer: Be CAREFUL with this one. The car has the SAME mass each time but the change in VELOCITY is much different! Impulse is both Ft and m(delta)v. For car A, the change in velocity is 9 m/s (since it actually reverses direction) and the change in velocity for car B is only 5 m/s.
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