Question
A variable force 
acts on a body. Write an expression for the work done in displacing the body from 
Can we find the work from F versus x graph?
Solution
Work done by a variable force is calculated by calculus method.
Let at any instant, the position of body be 
and the force on the body be 
.
The work done in displacing the body by small displacement 
is,
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is,
Graphically the work done by a variable force is equal to area under force versus displacement graph.
