(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A plank having length L and mass M rests in equilibrium on two supports (1 and 2) that are separated by a distance D. The supports are located at equal distances from the enter of the plank. A mass m hangs from the right end of the plank. If L=6m and D=2m, which of the following expressions correctly describes the normal force N1 that support 1 exerts on the plank:

N1=Mg+mg

N1=Mg-mg

N1=Mg/2+mg

N1=Mg/2-mg

N1=Mg-mg/2

2. Relevant equations

ƩT = Iα = rF where T is torque, I is moment of inertia, α is angular acceleration, r is a distance, F is a force.

3. The attempt at a solution

I know the answer is the second to last one but I can't figure out why. I don't understand what happened to N2 and I'm not sure how Mg/2 is derived and I keep messing up the signs. This is probably an easy problem I'm just having a lot of trouble figuring it out. Any help is much appreciated!

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# Homework Help: Static equilibrium mass and plank problem

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