There are two different numbers. The work done ON the stereo is
(11*0.75*9.8) J
The work of raising his own CM is
(50*0.40*9.8) J
A 50 kg boy picks up a 11 kg stereo and raises it 0.75 m from the floor to a tabletop. How much work did he do on the stereo? How much work did he do to raise his own center of mass 0.40 m in the process?
I'm assuming you use W=mgy equation but do you consider the weight of the stereo when solving it??
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