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?

A

If the force is applied at point P tangentially then $$\tau$$ decreases continuously as the wheel climbs

B

If the force is applied normal to the circumference at point X then $$\tau$$ is constant

C

If the force is applied normal to the circumference at point P then $$\tau$$ is zero

D

If the force is applied tangentially at point S then $$\tau\neq0$$ but the wheel never climbs the step