Question

A rope is used to lower vertically a block of mass M at a distance x at a constant downward acceleration $g/2$. The work done by the rope on the block is:

• A. Mgx
• B. $\frac{1}{2}Mg{x}^2$
• C. $-\frac{1}{2}Mgx$
• D. $Mg{x}^2$

Answer 1

The correct option is C $-\frac{1}{2}Mgx$

$mg-T=\frac{mg}{2}\Rightarrow T=\frac{mg}{2}$
W.D by rope $=-Tx$
$=-mg\frac{x}{2}$