# Easy statics problem

1. Nov 8, 2009

### walnuts

1. The problem statement, all variables and given/known data

Figure 12-61 is an overhead view of a rigid rod that turns about a vertical axle until the identical rubber stoppers A and B are forced against rigid walls at distances rA = 7.0 cm and rB = 3.2 cm from the axle. Initially the stoppers touch the walls without being compressed. Then force of magnitude 110 N is applied perpendicular to the rod at a distance R = 5.6 cm from the axle. Find the magnitude of the force compressing (a) stopper A and (b) stopper B.

The distance R is between the axle and stopper A.

2. Relevant equations

torque(net)=0

3. The attempt at a solution

For statics I usually pick a pivet point, but since there is an axle will I have to use that as reference?

using the stopper at rB as the pivet point.
Fb= force on stopper b
Fa=force on stopper a
F=applied force

Fb*(rB) + F*(rB+R)-Fa*(rA+rB)=0

F*(rB+R)=Fa*(rA+rB)

(F*(rB+R))/(rA+rB)=Fa

Fa-F=Fb

and it's wrong. [/b]

Last edited: Nov 8, 2009