Question

question 9 (1 point)
a block of mass m slides down a frictionless plane inclined at an angle θ with the horizontal. the normal reaction force exerted by the plane on the block is directed
○ parallel to the plane in the same direction as the movement of the block.
○ parallel to the plane in the opposite direction as the movement of the block
○ perpendicular to the plane.
○ toward the center of the earth.

Explanation:

The normal force is a contact force that acts perpendicular to the surface of contact. For a block on an inclined plane, the plane exerts a normal force on the block that is perpendicular to the plane's surface. The first two options are incorrect because normal force is not parallel to the plane. The last option is incorrect because the normal force is perpendicular to the plane, not necessarily toward the Earth's center (the gravitational force has a component toward the center, but normal force is about the contact surface).

Answer:

C. perpendicular to the plane.