A block of mass m is suspended by a light thread from an elevator… - Vidyadip

MCQ

A block of mass $m$ is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration $a$ . The work done by tension on the block during $t$ seconds is $(u = 0)$

✓
$\frac{m}{2}\left( {g + a} \right)a{t^2}$
B
$\frac{m}{2}\left( {g - a} \right)a{t^2}$
C
$\frac{m}{2}g\,a{t^2}$
D
$0$

✓

Answer

Correct option: A.

$\frac{m}{2}\left( {g + a} \right)a{t^2}$

a
$\mathrm{T}=\mathrm{mg}+\mathrm{ma}, \quad \mathrm{S}=\frac{1}{2} \mathrm{at}^{2}$

$\mathrm{W}_{\mathrm{T}}=\mathrm{T} \times \mathrm{S}$

$=\frac{\mathrm{m}(\mathrm{g}+\mathrm{a}) \mathrm{at}^{2}}{2}$

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