Question

Two masses $m_{1}=5\,kg$ and $m_{2}=4.8\,kg$ tied to a string are hanging over a light frictionless pulley. What is the acceleration of the masses when lift is free to move ? $(g=9.8 \, m/s^{2})$

• A. $0.2\,m/s^{2}$
• B. $9.8\,m/s^{2}$
• C. $5\,m/s^{2}$
• D. $4.8\,m/s^{2}$

Answer 1

Answer: (A)

$0.2\,m/s^{2}$

Answer 2

On releasing, the motion of the system will be according to figure. $m_{1} g-T=m_{1} a \ldots$ (i) and $T-m_{2} g=m_{2} a \ldots$ (ii) On solving; $a=\left(\frac{m_{1}-m_{2}}{m_{1}+m_{2}}\right) g ....$(iii) Here, $m_{1}=5 \,kg , m_{2}=4.8 \,kg , g=9.8\, m / s ^{2}$ $\therefore a=\left(\frac{5-4.8}{5+4.8}\right) \times 9.8$ $=\frac{0.2}{9.8} \times 9.8=0.2\, m / s ^{2}$