Answers

2016-02-06T21:09:04+05:30
when we lift an object 2 forces acts on it these are:
(I) muscular force
and
(II) gravitational force
a. positive work is done by the muscular force because the displacement is in the direction of the muscular force .
b. negative work is down by the gravitational force because displacement is in the opposite direction to which the gravitational force is acting ... 
i hope it helps....
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