Horizontal Pulley System

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1. Nov 1, 2016

Haniah

1. The problem statement, all variables and given/known data
A group of construction workers are building a house and want to lower down an excess bundle of 1400 kg bricks to ground. They tie one end of a rope to the bundle of bricks, loop it through a pulley, and tie the other end of the rope to a toolbox. If the coefficient of kinetic friction between the toolbox and the floor is 0.690 and the acceleration of the bundle of bricks is 4.56 m/s2, what is the mass of the toolbox?
where A=toolbox
and B=bricks

2. Relevant equations
T-ukmBg=-mBaA
T-mAg=mAaA
(mA-ukmB)g=-(mA+mB)aA
3. The attempt at a solution
mA = ((gukmB)-(amB))/(a+g)
I tried to solve by using this rearranged formula but did not get the right answer. I'm not quite sure what I'm doing wrong or what I'm missing. I am also assuming that acceleration (4.56 m/s2) is uniform, is this a correct assumption.

2. Nov 1, 2016

Staff: Mentor

I think you have your A and B reversed. Also, check your signs. (Let "a" be the magnitude of the acceleration.)