Question

A solid sphere of mass $10kg$ is placed on rough surface having coefficient of friction $\mu =0.1$ A constant force $F=7N$ is applied along a line passing through the centre of the sphere as shown in the figure. The value of frictional force on the sphere is

• A. $1N$
• B. $2N$
• C. $3N$
• D. $7N$

Answer 1

Answer: (B)

$2N$

$f_{max}=\mu mg=0.1\times 10\times 10=10N$
Requirement of friction $a=R\alpha$
$\therefore \left(\frac{7-f}{10}\right)=\frac{\left(R\right)(f\cdot R)}{2/5m{R}^2}=\frac{2.5f}{m}=\frac{2.5f}{10}$
Solving this equation, we get $f=2$
Since, $f<f_{max}$ therefore $2N$ frictional force will act