# Tension and sliding rod

1. Sep 8, 2013

### Woopydalan

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

2. Relevant equations

3. The attempt at a solution

So I am thinking about this problem, and what I don't understand is how at that point A, it is below the x-z plane, but it is not given how far below it is. If I knew, I could solve for the tension in the y-direction and set it equal to the weight.

I must be able to use c and 8 in. to get me closer to that distance below the x-z plane, but I'm not sure how

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2. Sep 8, 2013

### PeterO

use 3-D Pythagoras to calculate how far below the x-z plane the mass is each time. remember, the two masses are 18" apart.

If you don't understand 3-D Pythagoras, use normal Pythagoras on the 8" and c to find the direct distance across that void, the normal Pythagoras with the 18" cable/rod (or what ever it was) to calculate how far below the x-z plane A was in each case.

Last edited: Sep 8, 2013
3. Sep 8, 2013

### TSny

If (xA, yA, zA) and (xB, yB, zB) are the coordinates of A and B, respectively, how can you express the length of the wire in terms of these coordinates?

4. Sep 8, 2013

### Woopydalan

Here is my attempt

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5. Sep 8, 2013

### TSny

Your work looks good, except you seem to have made a mistake in the final evaluation of T in part (a).