Question

1. friction always acts: a) in the same direction as motion b) in the opposite direction of motion c) upward toward the sky d) only when objects are at rest

Explanation:

Friction is a force that opposes relative motion between two surfaces in contact. For an object in motion (like a sliding block), friction acts opposite to the direction of its motion. Option a is wrong as friction opposes, not aids, motion direction. Option c is wrong as friction is parallel to surfaces, not vertical upward. Option d is wrong as friction exists for moving objects (kinetic friction) and also for objects at rest (static friction, opposing impending motion), so it's not only when at rest. So the correct option is b.

Answer:

b) In the opposite direction of motion