Answer:
When
the thin wheel is rolling upright, it possesses some angular momentum in the
horizontal direction along the axis of the wheel. As angular momentum is
conserved in magnitude as well as direction (in the absence of external torque)
the wheel cannot fall from its upright position. However, when external torque
due to friction reduces angular velocity of the wheel of to zero, (i.e. when
the wheel becomes stationary) it falls from its upright position at the
slightest disturbance, on account of moment of force due to its weight.
You need to login to perform this action.
You will be redirected in
3 sec