# Solving Newton's Laws: Find Friction Force on Block A

• Dolly

## Homework Statement

Block A in the figure weighs 65.9N. The coefficient of static friction between the block and the surface on which it rests is 0.27. The weight w is 12.2N and the system is in equilibrium.

block A is placed on a table, it is connected by a string to a wall block w is hung off that string to form a 90degree angle between A and w and a 45degree angle between w and the wall.

A) Find the friction force exerted on block A.

Fr = u Fn
F = ma

## The Attempt at a Solution

i tried to find the net force using f = ma but there is no horizonal acceleration... so i am confused. :S help??

There is no horizontal acceleration, but there is an acceleration due to gravity on block W.

First you need to calculate the static force of friction on block A:
F=UsFn
F=(0.27*65.9)
F=17.793

Then you need to determine if the tension on the string from block W has enough force to move block A:
F(b)=MA
F(b)=12.2(9.8)
F(b)=119.56