Question

Find the frictional force acting on the body if it performs pure rolling.

• A. $\frac{20}{3}$
• B. $\frac{10}{3}$
• C. $\frac{5}{3}$
• D. None of these

Answer 1

The correct option is B $\frac{10}{3}$

According to the concept of rotational equilibrium,
torque is acting on whole body with respect to stable & unstable equilibrium
total force F = ma
$\tau$ = $r\times f=I\times \alpha$
$F\left(R\right)-f\left(2R\right)=4\left(\frac{a}{2R}\right)$
$R(F-2f)=4\left(\frac{a}{2R}\right)$
$F-2f=2a$

We will consider f = 2a, total force acting on body ,"a" is acceleration due to gravity.
$F-2f=f$
$F=3f,$ now $f=\frac{F}{3},f=\frac{10}{3}N$