We may choose to think of friction as a force rendering the collision between a superball and wall partially inelastic. The direction of the impulse given by friction to the ball when it strikes a wall obliquely (note that there exists relative motion in such a case between the ball and the wall in a direction parallel to the surface of the wall) is A) in the direction of the component of the ball motion parallel to the wall surface. B) opposite the direction of the component of the ball motion parallel to the wall surface. C) perpendicular to the direction of the component of the ball motion parallel to the wall surface and directed toward the wall. D) perpendicular to the direction of the component of the ball motion parallel to the wall surface and directed away from the wall.

Question

Quizplus · Accepted Answer

Friction always acts in the opposite direction to the relative motion between two surfaces. In this case, it opposes the component of the ball's motion that is parallel to the wall surface.

We May Choose to Think of Friction as a Force