Question

A cyclist is riding in the positive horizontal direction at 14.8 m/s on a horizontal level surface. He encounters an air resistance force of 50 N. The actions on the pedals by the cyclist cause a backward force of 73 N to be exerted by the rear wheel on the ground. The mass of the cyclist-bike system is 89 kg. calculate the horizontal acceleration of the center of mass of the system.

Answer 1

The net force on the bike and rider is
Fnet = 73 - 50 = 23 N.

The acceleration is a = Fnet/m = 23/89 = 0.258 m/s^2

The 73 N backward force of the bike on the road is another way of saying that the road pushes the bike tires forward with that force. That is because of Newton's third law.