SAT Subject Physics Practice Question 170: Answer and Explanation

Next steps

Question: 170

16. It refers to the collision of two blocks on a frictionless table. Before the collision, the block of mass m is at rest.

If the collision were elastic, what is the total kinetic energy of the blocks just AFTER the collision?

A. 16 J
B. 32 J
C. 64 J
D. 128 J
E. 256 J

Correct Answer: D

Explanation:

Using the equation K = mv2/2, we can figure out that before the collision, the kinetic energy of the left-hand block was (4 kg)(8 m/s)2/2 = 128 J and that of the right-hand block was zero (since it was at rest), giving a total kinetic energy before the collision of 128 J. Since kinetic energy is conserved in an elastic collision, the total kinetic energy after the collision must also be 128 J.

Previous       Next