Q.
Two masses $m_{1} = 5\ kg$ and $m_{2} = 4.8\ kg$ tried to a string are hanging over a light frictionless pulley. What is the acceleration of the masses when lift is free to move? $(g = 9.8\ {ms}^{- 2})$
A) $0.2\ {ms}^{- 2}$
B) $9.8\ {ms}^{- 2}$
C) $5\ {ms}^{- 2}$
D) $4.8\ {ms}^{- 2}$
Explanation
(a) On releasing, the motion of the system will be according to figure,
$m_{1}g - T = m_{1}a$ ….(i)
$\ and\ {T - m}_{2}g = m_{2}a$ …(ii)
[image:5_image172.jpeg]
On solving:
$a = \left( \frac{m_{1} - m_{2}}{m_{1} + m_{2}} \right)g\ \ \ldots.(iii)$
$Here,\ m_{1} = 5\ kgi,\ m_{2} = 4.8\ kg,\ g = 9.8\ {ms}^{- 2}$
$\therefore\ \ \ \ a = \left( \frac{5 - 4.8}{5 + 4.8} \right) \times 9.8$
$= \frac{0.2}{9.8} \times 9.8 = 0.2\ {ms}^{- 2}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.