Question

$1kg$ and $4kg$ blocks lie on a rough horizontal surface. The coefficient of friction between $4kg$ block and surface is $0.2$ while the coefficient of friction between $1kg$ block and the surface is $0.6$. All the pulley shown in the figure are massless and frictionless and all strings are massless.

• A. The frictional force acting on $1kg$ block is $2N$.
• B. The frictional force acting on $1kg$ block is $6N$ .
• C. The tension in the string connecting $4kg$ block and $1kg$ block is $2N$.
• D. The tension in the string connecting $1kg$ block and $4kg$ block is zero.

Answer 1

The correct option is B The frictional force acting on $1kg$ block is $6N$ .

Here, $1kg$ and $4kg$ blocks lie on a rough horizontal surface.

For $2kg$ block:

$2T=20$

∴ Surface tension, $T=\frac{20}{2}=10N$

For $4kg$ block:

$4T=40N$

According to question, The coefficient of friction between $4kg$ block and surface is $\mathrm{0.2.}$

∴ $f_s=0.2\times 40N$

$=8N$

Similarly, For $1kg$ block:

$1T=1\times 10$

$=10N$

Here, the coefficient of friction between 1kg block and the surface is 0.6.

∴ $f_s=0.6\times 10N$

$=6N.$

Thus, The frictional force acting on $1kg$ block is $6N.$