# Equilibrium of two rods

1. Mar 24, 2012

### songoku

1. The problem statement, all variables and given/known data
Weight of AB = CD = 200 N
Length of AB = 3 m
Length of CD = 2 m
A boy moves from point A toward B. At what distance from point A the rod will topple?
a. 0.4 m b. 0.5 m c. 0.6 m d. 1 m e. 2 m

2. Relevant equations
newton's law
torque

3. The attempt at a solution
When rod AB topples, the normal force at B = normal force at C = 0 right?

Will there be normal force at point A? Where should I take the pivot?

Thanks

2. Mar 24, 2012

### ehild

What is the boy's weight?
The rod AB topples only when DC does it. It happens when the torque of the weight of DC around E can not balance the torque arising from the other rod. In that case the support C does not exert force. Put the pivot of rod DC at E.

ehild

3. Mar 24, 2012

### songoku

Oh I'm sorry. The boy's weight is 600 N. Is 0.5 m the correct answer? Thanks

4. Mar 24, 2012

### ehild

I got the same.

ehild

5. Mar 24, 2012

### songoku

Thanks for the help :)