Answer to Question #90655 in Mechanics | Relativity for Bipin

Question

A ring of mass 3 kg and a block of mass 4 kg are in equilibrium. The string is light and pulley P does not offer any friction. The minimum coefficient of friction between pole and ring.

Answer 1

According to Newton's first law:

$$m_{block}g=F_{friction}$$

Also

$$F_{friction}=\mu N_{ring}=\mu m_{ring }g$$

So, we get

$$\mu=\frac{m_{block}}{m_{ring}}=\frac{4}{3}=1.33$$

Minimal coef. of friction is 1.33