Determine the direction of frictional forces (left, right, up down) for the objects:
1) A cup resting on top of a car. The car is moving and accelerating to the right.
2) A block being pushed to the right up an incline.
3)A block being placed at the middle of an incline (slope increasing to the right).
4)A cup sliding left across a table top
5) A book being pressed (force from the left) against a wall. The book is stationary.
1 answer
friction is in opposite direction to motion, or opposite direction to a force which is tending to motion. For instance, on 3), friction is up the incline, to the right. 5) friction is upward, as gravity trying to make downward motion exists.