# Pivot Points and Hanging Signs

1. Mar 31, 2009

### SpeedPhysics

1. The problem statement, all variables and given/known data
A 66 kg sign hung centered from a uniform rod of mass 8.2kg and length 2.3m. At one end the rod is attached to the wall by a pivot; at the other end it's supported by a cable that can withstand a maximum tension of 800 N. what is the minimum height h above the pivot for anchoring the cable to the wall?

2. Relevant equations

Not entirely sure if these apply.

$$\tau$$ = r x F
$$\tau$$ = $$\Sigma$$

3. The attempt at a solution

Mg = (74.2)(9.8) = 727.16 N (Total Fy)

$$\tau$$ = (2.3)*(727.16) = 1672.5

After I get this information I'm lost.

2. Apr 1, 2009

### tiny-tim

Welcome to PF!

Hi SpeedPhysics ! Welcome to PF!
(it's not 2.3 … the weight goes through the centre )

ok, that's the torque (the moment) of the weight …

now, if you call the tension T, what's the torque of the tension?