Question

select the statement that is always true of the normal force.
it is parallel to the surface.
it is it is in the opposite direction of the gravitational force.
it is perpendicular to the surface.
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Explanation:

The normal force is a contact force that acts perpendicular to the surface. For example, when an object is placed on a horizontal table, the normal force from the table on the object is vertical (perpendicular to the horizontal surface). If the surface is inclined, the normal force is still perpendicular to that inclined surface. It is not always parallel to the surface (so the first option is wrong). Also, it is not always in the opposite direction of the gravitational force. For example, on an inclined plane, the gravitational force has components along and perpendicular to the plane, and the normal force only counteracts the perpendicular component (so the second option is wrong). But by definition, the normal force is always perpendicular to the surface.

Answer:

It is perpendicular to the surface.