Answer
a). Suppose the ball skids to the right so the friction force will act on it in the opposite direction so as to prevent the ball from skidding.
Hence the torque exerted by friction about center of mass on the ball will be in clock-wise direction.
b). Friction force $=coefficient \times mg=0.4\times 7 \times 9.8 N=27.44N$
Torque due to friction about center of mass =$f\times r\times sin90^{\circ}=27.44\times\frac{17}{100}=4.66 Nm$
Work Step by Step
a). Suppose the ball skids to the right so the friction force will act on it in the opposite direction so as to prevent the ball from skidding.
Hence the torque exerted by friction about center of mass on the ball will be in clock-wise direction.
b). Friction force $=coefficient \times mg=0.4\times 7 \times 9.8 N=27.44N$
Torque due to friction about center of mass =$f\times r\times sin90^{\circ}=27.44\times\frac{17}{100}=4.66 Nm$
