question_answer

A mass m is lowered with the help of a cord of length d by a disc at a constant acceleration g/4 The work done by the cord will:

A)  \[\frac{3}{4}mgd\]                                         

B) \[\frac{mgd}{8}\]                            

C)  \[\frac{mgd}{4}\]          

D)         \[mgd\]

Correct Answer: C

Solution :

Work done    \[W=\overrightarrow{F}\times \overrightarrow{s}\]      \[=Fs\cos 0{}^\circ \]      \[=mad\]        \[(\because s=d)\] \[\frac{mgd}{4}\,\,\,\,\Rightarrow \,\,\,\,W=\frac{mgd}{4}\]