SAT Subject Physics Practice Question 257: Answer and Explanation
A small box slides down a frictionless track in the shape of a quarter-circle of radius R. The box starts from rest at the top of the track, a height equal to 2R above a horizontal surface. At the moment the box leaves the bottom of the track, a ball of the same mass as the box is dropped from the same height at the bottom of the track.
How fast is the box moving when it reaches the end of the track?
A. v =
B. v =
C. v =
D. v =
E. v =
Correct Answer: B
We’ll use conservation of mechanical energy. Let the flat surface be our PEgrav = 0 level. Then