posted by dominique .
Which direction will the support force by the wall point when the force diagram is drawn? The book is held motionless against a wall by yout hand. (Up, down, legt or right?)
1.You apply a force F on the book in horizontal direction towards the wall.
2. The normal reaction of the wall on the book will be (say) N. For equilibrium in horizontal direction =>
F = N
3. The weight of the book M*g will act on the book in downward direction.
4. The frictional force Fr= mu*N will act on the book in vertically upward direction.
For equilibrium in vertical direction =>
mu*N = M*g
(the static mu will adjust itself to satisfy the above expression)
You can draw the force diagram showing the four forces acting on the book. So, the wall provides two forces for support - the normal reaction N and the frictional force Fr.