A mass M is lowered with the help of a string by a distance h at a distance acceleration `g//2`. The work done by the string will be

Options

A. (a) `(Mgh)/(2)`
B. (b) `-(Mgh)/(2)`
C. (c) `(3Mgh)/(2)`
D. (d) `-(3Mgh)/(2)`

Answer

B

Explanation

Tension in the string,
`T=M(g-a)=M(g-g/2)=Mg`
W=Force x Depression=-M(g/2)g`
Negative sign is because tension is in the upward direction and displacement is in the downward direction.