SAT Subject Physics Practice Question 500: Answer and Explanation
1. A magician pulls a tablecloth from under a table full of dishes without disturbing the dishes. This act demonstrates that
A. gravity holds the dishes still.
B. the weight of the dishes is reduced.
C. action-reaction forces are in operation.
D. the dishes have inertia.
E. the dishes have no acceleration.
Correct Answer: D
The correct answer is (D). The inertia of the dishes (Newton's first law) causes them to remain at rest. The fast rate at which the magician pulls the tablecloth from under the dishes keeps the static friction from changing to kinetic friction.