http://www.ck12.org Chapter 7. Momentum Conservation
a. What happens to the speed of the train when it releases the last boxcar? (Hint: Think before you blindly
calculate.)
b. If the train can shoot boxcars backwards at 30 m/srelative to the train’s speed,how many boxcars does
the train need to shoot out in order to obtain a speed of 58.75 m/s?- In Sacramento a 4000 kg SUV is traveling 30 m/s south on Truxel crashes into an empty school bus, 7000 kg
traveling east on San Juan. The collision is perfectly inelastic.
a. Find the velocity of the wreck just after collision
b. Find the direction in which the wreck initially moves - Manrico( 80 .0 kg)and Leonora( 60 .0 kg)are figure skaters. They are moving toward each other. Manrico’s
speed is 2.00 m/s; Leonora’s speed is 4.00 m/s. When they meet, Leonora flies into Manrico’s arms.
a. With what speed does the entwined couple move?
b. In which direction are they moving?
c. How much kinetic energy is lost in the collision?
Answers to Selected Problems- 2.0 kg, 12 .5 m/s
- 0.13 m/s to the left
- a. no change b. the last two cars
- a.15 m/s b. 49◦S of E
- a. 0.57 m/s b. the direction Leonora was originally travelling c. 297.26 J
Summary
In this chapter students learn how to analyze and solve momentum questions and problems. Specifically, they will
learn about momentum conservation in the context of collisions and also about impulse and impulse force.