A block of mass `5kg` is being raised vertically upwards by the help of a string attached to it. It rises with an acceleration of `2ms^-2`. Find the work done by the tension in the string if the block rises by `2.5m`. Also find the work done by the gravity and the net work done.

Explanation

Let us first calculate the tension
From force diagram :

`T - mg = 5a`
`T = 5(9.8 + 2) = 59 N`
As the string force T and displacement `vec S` are in same direction (upwards), work done by the tension T is `W = TS = 59 (2.5) = 147.5 J`
Work done by the gravity ` = - mgs = - 5(9.8)(2.5) = -122.5 J`
Net work done on block = work done by T + work done by mg `= 147.5 + (-122.5) = 25 J`