A heavy wooden block is dragged by a force along a rough steel plate, as shown below for two cases. The magnitude of the applied force is the same for both cases. The normal force in (ii), as compared with the normal force in (i) is:
A) the same
B) greater
C) less
D) less for some angles of the incline and greater for others
E) less or greater, depending on the magnitude of the applied force

Question

A heavy wooden block is dragged by a force  along a rough steel plate, as shown below for two cases. The magnitude of the applied force  is the same for both cases. The normal force in (ii), as compared with the normal force in (i) is: 
A) the same 
B) greater 
C) less 
D) less for some angles of the incline and greater for others 
E) less or greater, depending on the magnitude of the applied force

Quizplus · Accepted Answer

In case (i), the block is on a horizontal surface, so the normal force is equal to the weight of the block. In case (ii), the block is on an inclined plane, so the normal force is less than the weight of the block. This is because a component of the weight is acting parallel to the surface of the plane, and is balanced by the frictional force, while the remaining component of weight acts perpendicular to the plane and is balanced by the normal force. Thus, the normal force in (ii) is less than the weight of the block and less than the normal force in (i).

A Heavy Wooden Block Is Dragged by a Force