Determine the direction of frictional forces (left, right, up down) for the objects:

Question

1) A cup resting on top of a car. The car is moving and accelerating to the right.

Up - This one I'm not sure but I think up because the frictional force would have to go up to hold the cup on the top of the car

2) A block being pushed to the right up an incline.

Left

3)A block being placed at the middle of an incline (slope increasing to the right).

Left

4)A cup sliding left across a table top

Right

5) A book being pressed (force from the left) against a wall. The book is stationary.

Right - This one I'm really not sure but I think it's right since the force is from the left.