Question

Two masses $A$ and $B$ of $5\text{kg}$ and $6\text{kg}$ are connected by a string passing over a frictionless pulley fixed at the corner of table as shown in figure. The coefficient of friction between $A$ and the table is $0.3$. The minimum mass of $C$ that must be placed on $A$ to prevent it from moving is equal to: $(\text{Take}=10{\text{m/s}}^2)$

• A. $15\text{kg}$
• B. $10\text{kg}$
• C. $5\text{kg}$
• D. $3\text{kg}$

Answer 1

The correct option is A $15\text{kg}$

At equilibrium,

$T=60N$ .......(1)
$T=\mu N$ (To prevent A from moving)
$T=\mu (5g+mg)$
$\Rightarrow \mu (50+10m)=60$
$\Rightarrow 50+10m=\frac{60}{0.3}=200$
$\Rightarrow m=15\text{kg}$