Question

Two blocks are connected over a massless pulley as shown in the figure. The mass of block $A$ is $10\text{kg}$. If block $A$ slides down the inclined plane at constant speed, then mass of block $B$ in $\text{kg}$ is

• A. $4$
• B. $3$
• C. $2$
• D. $5$

Answer 1

The correct option is D $5$

Given,
Block $A$ slides down with constant speed
$\Rightarrow$ Acceleration of block $A=$ Acceleration of Block $B=0$

From FBD of block $B$,
$T=m_{B}g$ ......$\left(i\right)$


From FBD of block A,
$T=m_{A}g\sin {30}^{\circ }$
$T=10\times 10\times 0.5\text{N}=50\text{N}$

From eq $\left(i\right)$, we get
$T=m_{B}g$
$50=m_{B}g$
$\therefore m_B=50/g=5\text{kg}$