Q. Two masses $m_{1} = 1kg$ and $m_{2} = 2kg$ are connected by a light inextensible string and suspended by means of a weightless pulley as shown in figure.

Assuming that both the masses start from rest, the distance travelled by the centre of mass in 2 s is $(take\ g = 10m/s^{2})$

A) $\frac{20}{9}m$
B) $\frac{40}{9}m$
C) $\frac{2}{3}m$
D) $\frac{1}{3}m$
Explanation

(a) $Given,\ m_{1} = 1kg,\ m_{2} = 2\ kg\ and\ g = 10m/s^{2}$
$a = \left( \frac{m_{2} - m_{1}}{m_{1} + m_{2}} \right)g$
$= \left( \frac{2 - 1}{1 + 2} \right)10 = \frac{10}{3}$
$S = \frac{1}{2}a\ t^{2}$
$= \frac{1}{2} \times \frac{10}{3} \times 4 = \frac{20}{3}$
$m = \frac{2 \times \frac{20}{3} - 1 \times \frac{20}{3}}{3} = \frac{20}{9}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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