Rolling Friction (Rolling Resistance)

Rolling Friction (Rolling Resistance)

• When a wheel rests on ground, both the wheel and the ground deform due to weight of the wheel as shown in Fig 8.8.1 (a).

• To move the wheel at constant speed a horizontal force P is required to be applied at the axle as shown in Fig. 8.8.1 (b).

• The resultant R of all forces exerted by ground on the wheel is experimentally found to be slightly in front of line of action of weight W.

• To roll the wheel at constant speed, the moment of W about A has to be balanced by moment of P about A.

⸫ Wb = Pr

• The length b is known as the coefficient of rolling resistance. A larger value of b makes P larger which indicates a larger effort to keep the wheel moving.