A Wheel of Radius R Is Rolling Without Slipping Down

Multiple Choice

A wheel of radius R is rolling without slipping down an inclined surface. The frictional force exerted by the surface on the wheel at the point where the rim is in contact with the surface is

A) tangent to the surface, pointing in the same direction as the velocity of the center of mass.
B) tangent to the surface, pointing in the direction opposite that of the velocity of the center of mass.
C) zero.
D) normal to the surface, pointing toward the wheel's center of mass.
E) normal to the surface, pointing away from the wheel's center of mass.