A light inextensible string that goes over a smooth fixed pulley … - Vidyadip

MCQ

A light inextensible string that goes over a smooth fixed pulley as shown in the figure connects two blocks of masses $0.36 \mathrm{~kg}$ and $0.72 \mathrm{~kg}$. Taking $g=10 \mathrm{~m} / \mathrm{s}^2$, find the work done (in joules) by the string on the block of mass $0.36 \mathrm{~kg}$ during the first second after the system is released from rest.

A
$5$
B
$6$
✓
$8$
D
$9$

✓

Answer

Correct option: C.

$8$

c
$2 mg - T =(2 m ) a$

$T - mg = ma$

$\Rightarrow a = g / 3$

$T =\frac{4 mg }{3}$

$w = T \times s = T \times \frac{1}{2} at ^2=\frac{4 mg }{3} \times \frac{1}{2} \times \frac{ g }{3} \times 1^2=\frac{200}{9} \times 0.36$

$=8 \text { Joules }$

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