A box slides down a frictionless plane inclined at an angle θ above the horizontal.The gravitational force on the box is directed
A) parallel to the plane in the same direction as the movement of the box.
B) parallel to the plane in the opposite direction as the movement of the box.
C) perpendicular to the plane.
D) vertically.
E) at an angle θ below the inclined plane.

Question

Quizplus · Accepted Answer

The gravitational force on the box is always vertically downwards, perpendicular to the inclined plane. This force can be resolved into two components, one parallel to the plane (mg*sinθ) and the other perpendicular to the plane (mg*cosθ). The parallel component is responsible for the motion of the box down the plane. Therefore, the correct answer is D.

A Box Slides Down a Frictionless Plane Inclined at an Angle