Homework Help: physics

Posted by Joseph on Wednesday, June 27, 2012 at 9:23pm.

A uniform horizontal bar of length L = 5 m and weight 243 N is pinned to a vertical wall and supported by a thin wire that makes an angle of theta = 39o with the horizontal. A mass M, with a weight of 300 N, can be moved anywhere along the bar. The wire can withstand a maximum tension of 600 N. What is the maximum possible distance from the wall at which mass M can be placed before the wire breaks?

I did (243x2) + 300x = 5*600 sin 39
x=4.67m but its incorrect and I dont know why ?

physics - MathMate, Thursday, June 28, 2012 at 8:38pm
You're almost there.
The length of the bar is 5m.
In general, we assume the centroid to be in the middle, or 2.5 m from the wall.
You have put in 243*2.0 instead of 243*2.5
I'm sure you'd be OK after this correction.

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