A wheel of radius R and mass M is placed at the bottom of a fixed step of height R as shown in the figure. A constant force is continuously applied on the surface of the wheel so that it just climbs the step without slipping. Consider the torque `tau` about an axis normal to the plane of the paper passing through the point Q. Which of the following options is/are correct?

Options

A. If the force is applied at point P tangentially then ` tau` decreases continuously as the wheel climbs.
B. If the force is applied tangentially at point S then ` tau ne 0 ` but the wheel never climbs the step.
C. If the force is applied normal to the circumference at point P then ` tau` is zero.
D. If the force is applied normal to the circumeference at point X then ` tau` is constant.

Answer

C, D