Question

When a bicycle is in motion and pedalled, the force of friction exerted by ground on the two wheels is such that it acts

• A. In the backward direction on the front wheel and in the forward direction on the rear wheel
• B. In the forward direction on the front wheel and in the backward direction on the rear wheel
• C. In the backward direction on both the front and rear wheels
• D. In the forward direction on both the front and rear wheels

Hint:

Think of it this way: the rear wheel pushes the ground back, so the ground pushes the wheel forward. The front wheel is just along for the ride, and the ground resists its forward motion.

Answer 1

The Correct Option is A

1. The Rear Wheel (Driving Wheel): When you pedal, the chain transmits torque to the rear wheel, causing it to attempt to rotate clockwise. The point of contact of the rear tire tries to slide

backward relative to the road. Friction opposes this relative motion; therefore, the ground exerts a static friction force in the

forward direction on the rear wheel. This is the force that actually propels the bicycle forward.

2. The Front Wheel (Driven Wheel): The front wheel is not connected to the pedals. It moves forward because the rest of the bicycle (the frame) pushes it forward. As the front wheel moves forward, the point of contact with the ground tries to slide

forward relative to the road. Friction opposes this forward sliding tendency, resulting in a friction force acting in the

backward direction on the front wheel. This friction is what causes the front wheel to rotate.

3. Summary:

• Rear Wheel: Friction acts forward (propulsion).

• Front Wheel: Friction acts backward (rotation resistance).
This is why the bicycle accelerates forward when pedalled.