Final answer:
Motorcycles lean to the left when the right handlebar is pulled back lightly due to inertia and conservation of angular momentum.
Step-by-step explanation:
In physics, motorcycles are subject to the laws of motion and balance. When a motorcycle is in motion, it is affected by several forces such as gravity, friction, and centripetal force.
When a physics student pulls back lightly on the right handlebar while driving at highway speed, it causes the motorcycle to tilt to the left. This happens due to the effect of inertia and the principle of conservation of angular momentum.
As the student pulls back on the right handlebar, it creates a slight torque or moment about the vertical axis, causing the motorcycle to lean to the left. This shift in weight distribution helps the motorcycle turn to the left.