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.
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.
1) The cup resting on top of the car will experience a frictional force pointing downward, towards the car. This is necessary to prevent the cup from sliding off the car due to its inertia.
2) The block being pushed to the right up an incline will experience a frictional force pointing to the left, opposite to the direction of the applied force. This is because the frictional force acts to oppose the motion of the block and prevent it from sliding down the incline.
3) The block being placed at the middle of an incline will initially experience no frictional force since it is not moving. However, if the slope starts increasing to the right, then the block will eventually start to move downwards, and the frictional force will act to oppose this motion. Therefore, the direction of the frictional force will be to the left.
4) The cup sliding left across a tabletop will experience a frictional force pointing to the right, opposite to its direction of motion. This force acts to slow down the cup and eventually bring it to a stop.
5) The book being pressed against a wall will experience a frictional force pointing to the right, opposite to the direction of the applied force. This frictional force acts to prevent the book from sliding along the wall.
1) The direction of the frictional force on the cup resting on top of a car depends on the relative motion between the cup and the car. If the car is moving and accelerating to the right, the cup tends to stay at rest due to inertia. Therefore, the frictional force on the cup would act in the opposite direction to the motion of the car, which is to the left. So, the direction of the frictional force on the cup is to the left.
2) When a block is being pushed to the right up an incline, the frictional force opposes the motion of the block. In this case, the block is being pushed up the incline, so the frictional force acts opposite to the direction of motion. Therefore, the direction of the frictional force is to the left.
3) When a block is placed at the middle of an incline with the slope increasing to the right, the block tends to slide down the incline due to the force of gravity. The frictional force acts to prevent the block from sliding down. Since the slope is increasing to the right, the block will tend to move towards the left if it starts sliding. Therefore, the direction of the frictional force is to the left.
4) When a cup is sliding left across a tabletop, the frictional force acts to oppose the motion of the cup. In this case, the cup is sliding to the left, so the frictional force acts opposite to the direction of motion. Therefore, the direction of the frictional force is to the right.
5) When a book is pressed against a wall with a force from the left and the book is stationary, the frictional force acts to prevent the book from sliding down the wall. Since the force is applied from the left, the frictional force will act to oppose this force and keep the book stationary. Therefore, the direction of the frictional force is to the right.