University:
College
Course:
College Physics
Academic year:

2022
Views:

71

Pages:

2
Author:

StellarSymphony

Name Class Date Concept-Development Practice Page Momentum 1. A moving car has momentum. If it moves twice as fast, its momentum twice is as much. 2. Two cars, one twice as heavy as the other, move down a hill at the same speed. Compared to the lighter car, the momentum of the heavier car is twice as much. 3. The recoil momentum of a cannon that kicks is (more than) (less than) (the same as) the momentum of the cannonball it ﬁres. *Although the speed and acceleration of the cannonball are greater. 4. If a man ﬁrmly holds a cannon when ﬁred, then the momentum of the cannonball is equal to the recoil momentum of the (cannon alone) (cannon–man system) (man alone). 5. Suppose you are traveling in a bus at highway speed on a nice summer day and the momentum of an unlucky bug is suddenly changed as it splatters onto the front window. a. Compared to the force that acts on the bug, how much force acts on the bus? (more) (the same) (less). b. The time of impact is the same for both the bug and the bus. Compared to the impulse on the bug, this means the impulse on the bus is (more) (the same) (less). c. Although the momentum of the bus is very large compared to the momentum of the bug, the change in momentum of the bus, compared to the change of momentum of the bug is (more) (the same) (less). d. Which undergoes the greater acceleration? (Bus) (Both the same) (Bug) e. Which, therefore, suffers the greater damage? (Bus) (Both the same) (The bug of course!) 6. Granny whizzes around the rink and is suddenly confronted with Ambrose at rest directly in her path. Rather than knock him over, she picks him up and continues in motion without “braking.” Consider both Granny and Ambrose as two parts of one system. Since no outside forces act on the system, the momentum of the system before collision equals the momentum of the system after collision. a. Complete the before-collision data in the table below. BEFORE COLLISION Granny’s mass 80 kg Granny’s speed 3 m/s 240 kg·m/s Granny’s momentum Ambrose’s mass 40 kg Ambrose’s speed 0 m/s Ambrose’s momentum 0 240 kg·m/s Total momentum b. After collision, does Granny’s speed increase or decrease? Decrease c. After collision, does Ambrose’s speed increase or decrease? Increase d. After collision, what is the total mass of Granny + Ambrose? 120 kg e. After collision, what is the total momentum of Granny + Ambrose? 240 kg·m/s f. Use the conservation of momentum law to ﬁnd the speed of Granny and Ambrose together after collision. (Show your work in the space below.) Mv + mv’ = (M + m)V (80 kg)(3 m/s) + 0 = (80 kg + 40 kg)V 240 kg·m/s = (120 kg)V V = 2 m/s New speed = 2 m/s