Suppose you take off in a car with your physics book on top. If you are accelerating forward and the book rides with you, in what direction does friction act on the book?
A) backwards
B) forwards
C) There is no friction since there is no sliding.
D) The force of friction is infinite.

Question

Quizplus · Accepted Answer

Friction acts in the opposite direction of the relative motion between surfaces. Since the car accelerates forward, the book tends to slide backward relative to the car. Therefore, friction acts forward on the book to prevent it from sliding off.

Suppose You Take Off in a Car with Your Physics