Case I: Two identical cars, each traveling at 30 mph, approach each other in a head-on totally inelastic collision. Case II: An automobile, traveling at 60 mph, hits an indestructible brick wall (mounted in concrete, so that it remains essentially unmoved) head-on, undergoing a totally inelastic collision. The ratio of the total kinetic energy before collision in the two cases (II to I-that is, TKE_II/TKE_I) is equal to A) 1/4. B) 1/2. C) 2. D) 4.

Question

Quizplus · Accepted Answer

In a totally inelastic collision, the total kinetic energy before the collision is equal to the total internal energy after the collision. In Case I, the total kinetic energy before the collision is 2(1/2)mv^2 = mv^2. In Case II, the total kinetic energy before the collision is (1/2)mv^2. Therefore, the ratio of the total kinetic energy before collision in the two cases (II to I-that is, TKE_II/TKE_I) is TKE_II/TKE_I = (1/2)mv^2/mv^2 = 1/2.

Case I: Two Identical Cars, Each Traveling at 30 Mph