Question

A disc of mass $m$ is connected to an ideal spring of force constant '$k.$' If the disc is released from rest then what is maximum friction force on the disc (in N). Assuming friction is sufficient for pure rolling.

Answer 1

Since the spring force increases as the disc starts rolling, the friction force which is self adjustable, decreases gradually. Hence maximum friction is observed when the disc is about to start rolling which is equal to

$F_{max}=\mu \left(mg\right)cos\theta$