Physics quiz question: elastic collision

Physics 5A Quiz 4, Fall Semester 2007
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Problem 7.48

[3.0 points.] A 0.250 kg airtrack cart traveling at 1.50 m/s in the +x direction collides elastically with a stationary cart of 0.075 kg. After they collide, the 0.075 kg cart has a final velocity of +2.31 m/s. Consider frictional forces between the carts and the airtrack to be negligible. What is conserved for this collision?
(A) Momentum only.
(B) Kinetic energy only.
(C) Both momentum and kinetic energy.
(D) (Neither momentum nor kinetic energy are conserved for this collision.)

Correct answer: (C)

Since there are no external horizontal impulses, momentum is conserved. By definition, kinetic energy is conserved for an elastic collision.

Student responses
Sections 0906, 0907
(A) : 4 students
(B) : 6 students
(C) : 28 students
(D) : 2 student