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Home  >>  JEEMAIN and NEET  >>  Physics  >>  Class11  >>  Work, Power and Energy

A cord is used to lower vertically a block of mass M,a distance d, at a constant downward acceleration $g/4$. Then work done by cord on block

\[(a)\;\frac{-3Mgd}{4} \quad (b)\;\frac{Mgd}{4} \quad (c)\; \frac{3Mgd}{4} \quad (d)\;Mgd\]

1 Answer

Let T be tension in the string
$Mg-T=\large\frac{Mg}{4}$
$T=Mg-\large\frac{Mg}{4}$
$\quad=\large\frac{3 Mg}{4}$
Work done by tension
$\quad=-T \times d$
$\quad =\large\frac{-3Mg}{4} $$\times d$
$\quad=\large\frac{-3Mgd}{4}$
Hence a is the correct answer
answered Aug 6, 2013 by meena.p
edited Jun 11, 2014 by lmohan717
 

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