# Uniform plank question?

## Homework Statement

A uniform plank 10m long and of mass 40kg is supported by two posts...?
A uniform plank 10m long and of mass 40kg is
supported by two posts, the first 1m from the left
end and the other 6m from the left end. A mass of
10kg is placed 8m from the left end. Find the force
each of the support posts exerts on the plank if it is
in equilibrium.

I'm not looking for just an answer. I would appreciate it you could tell me what needs to be done.

Here is the illustration that goes along with the question. http://i55.tinypic.com/2s61zj8.png

T= F x ℓ

## The Attempt at a Solution

Torque on the left: T = F2 x 1m (CCW)
Torque on the plank: T = -400N x 5m (CW)
Torque by the weight T= -100N x 7m (CW)

I really don't know where to go on from there. This is my first year in physics and i'm having trouble.

## The Attempt at a Solution

ideasrule
Homework Helper
Torque on the left: T = F2 x 1m (CCW)
Torque on the plank: T = -400N x 5m (CW)
Torque by the weight T= -100N x 7m (CW)
Before calculating torque, you have to decide which point you're using to calculate torque. You seem to have chosen the leftmost point of the plank, which is perfectly fine, as long as you're aware of it.

Your torque calculations are all correct, provided that you define the counterclockwise direction to be positive. You also need to calculate the force exerted by the second support.

I really don't know where to go on from there. This is my first year in physics and i'm having trouble.
In order for the system to be in equilibrium, torques and forces both have to sum to 0. For forces, write out Newton's second law, taking into consideration the directions of all the forces.
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