Calculating Acceleration of a Pulley Off 6-Story Building

[vericolorful]

Homework Statement

There is a pulley suspended off a 6 story building. One side of the pulley is attached to a mass of 250lb and the other 130lb. What's the acceleration?

Homework Equations

a=[(m2-m1)/(m2+m1)]g
g = 32 ft/s2

The Attempt at a Solution

Well, I think I'm suppose to use the equation listed above because it's linked with a atwood's machine lab we just did. I got the answer of -10.1ft/s2. I don't know if this is correct because my teacher said something about taking into the account of how high the building is. Each story is 10 ft. Thanks in advance.

 

[Dick]

You could also work it out just using a free body diagram. The equation for atwood's machine isn't so important you want to memorize it. The answer is correct, though I'm not sure why you included the minus sign. One weight is accelerating up and the other down. What could the minus add to that? I think your teacher was teasing you by suggesting the height of the building is a factor. How could it be? Don't believe that every number given in a problem statement is necessary to the solution of the problem.