Friction is a force that acts which of the following in relation to movement?

• A. In an opposite direction to movement
• B. In the same direction as movement
• C. Only when stationary
• D. Perpendicular to movement

Answer: (A)

Friction is the resisting force between surfaces in contact, and it always acts to oppose relative motion. When an object slides, friction points opposite to its direction of movement, slowing it down. If the object is at rest and an external force tries to move it, static friction acts opposite to that impending motion up to a limit to prevent slipping. Friction acts parallel to the contact surface, not perpendicular, and never in the same direction as movement. So the correct idea is that friction acts opposite to movement.