Question

suppose your writing desk is tilted a little. a book kept on it starts sliding down .show the direction of frictional force acting on it.

Answer 1

the direction of frictional force acting is opposite to the motion of book that is upwards

Answer 2

Answer:

When a book slides on the writing desk, a frictional force acts between the book and the surface of the desk. The direction of frictional force on the book is opposite to the direction of its motion and acts in upward direction, as shown in the figure alongside.