Solving a Problem: Find Mass of Box, Given Two Wire Support Beam Data

[pkossak]

I really could use help on this one! I got this one wrong on the last test, it was driving me crazy. Spent almost half the time trying to figure it out.

Two wires support a beam of length L=16. A box hangs from a wire which is connected a distance of 12 m from the left edge of the beam. The tension in the left support wire is 500 N and the tension in the right support wire is 600 N. What is the mass of the box? DATA: acceleration of gravity=9.80 m/s2

My next test is today, thank you incredibly much if you can help me figure out what I was doing wrong here.

 

[Doc Al]

Tell us what you did. (Are you given the mass of the beam? Is it uniform? Are the support wires vertical?)

 

[pkossak]

Not given the mass of the beam, yes the support wires are vertical.

The figure can be seen here http://www.msu.edu/~kossakze/physics.gif

The way I approached it was to consider the middle of the beam at m = 0. The left wire is at 8 m and 8 m*500 N + 4 m*x N (weight of box) = 8 m*600 N

nevermind...wow...got the answer, guess I didn't do that on the test.

Thanks anyway

 

[Doc Al]

Good. As long as the wires are vertical and beam is uniform, no problem. Just set up your equations for equilibrium.