Physics 5A Quiz 4, Spring Semester 2008
Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Problem 7.52
[3.0 points.] A Physics 5A student of mass 69.0 kg is at rest on ice skates. A 4.30 kg sled slides across the ice towards her. The sled is moving horizontally at 15 m/s just before the student catches and holds onto it. Neglect friction and drag. 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: (A)
Since there are no external horizontal impulses, momentum is conserved. However, since there is deformation with no rebound and separation in this perfectly inelastic collision, kinetic energy is not conserved.
Student responses
Sections 4987, 4988
(A) : 27 students
(B) : 2 students
(C) : 5 students
(D) : 2 students
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