Vertical friction required of a block between two walls?

[lilmayo99]

Homework Statement

A block is held between two walls. One static, one applying a force. If the block weighs 5kg, and the coefficient of static friction between each wall and the block is 0.4, what horizontal force is required by the wall applying it?

Do both walls contribute an equal vertical friction force, equal to the force applied by one of the walls times the co-efficient of friction, or does only one? The force required will be halved if both walls contribute a vertical frictional force.

Homework Equations

F=mg
F=uR
u=0.4

The Attempt at a Solution

 

[stockzahn]

Do both walls contribute an equal vertical friction force, equal to the force applied by one of the walls times the co-efficient of friction, or does only one?

Hi,

you apply the horizontal force F on the block with one wall and it doesn't move ... what does that tell you about the force at the opposite side (the static wall) and the sum of the forces respectively?