Chapter 8, Problem 20Q

When a motorcyclist leaves the ground on a jump and leaves the throttle on (so the rear wheel spins), why does the front of the cycle rise up?

To determine

The reason why the front of the cycle rises up, when a motorcyclist leaves the throttle on (so the rear wheel spins)during a jump

Answer to Problem 20Q

Solution:

A torque is applied on the rear wheel by the engine when a motorcyclist leaves the ground on a jump. As the torque is applied to the rear wheel, an equal and opposite torque is applied by the rear wheel to the bike. Due to this the front of the bike rises up.

Explanation of Solution

The reason for this is the principle of conservation of angular momentum. When the rear wheel is made to spin by leaving the throttle on, the angular momentum of the bike-motorcyclist system tends to increase from its initial value. To balance it, the front wheel tries to move in the opposite direction, because of which it rises up.