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

Two supports, made of the same material and initially of equal length, are 2.0m apart. A stiff

board with a length of 4.0m and a mass of 10 kg is placed on the supports, with one support

at the left end and the other at the midpoint. A block is placed on the board a distance of

0.50m from the left end. As a result the board is horizontal. The mass of the block is:

A. zero

B. 2.3kg

C. 6.6kg

D. 10 kg

E. 20 kg

**2. Relevant equations**

∑F = 0 = N_{1} + N_{2} – mg – Mg

∑τ = 0 = -1/2 N_{1} + 1/2 N_{2} – 1/2 Mg

**3. The attempt at a solution**

Those equations above are a result of a free body diagram I drew. However, if I begin to solve the equation for m, I end up with an expression in terms of N_{1} (ie. 2N_{1} = mg). Is there enough information in the question? By the way, I’m calculating torque from the position where the mass is placed.

http://ift.tt/1jGGCRG