Final answer:
From a bicyclist's reference frame, a person standing on the sidewalk would appear stationary. The principle of countersteering explains why a motorcycle steers in the opposite direction when the handlebars are turned slightly one way. Turning on a bicycle involves the principles of centripetal force and balancing forces through the center of gravity.
Step-by-step explanation:
If you are standing on a sidewalk and observe a bicyclist passing by to your right, from the bicyclist’s reference frame, you would appear to be stationary with respect to them. This is because, in the bicyclist's reference frame, they are moving relative to the surroundings while you are not moving relative to their perspective.
When a physics student riding a motorcycle at highway speed pulls back lightly on the right handlebar and the cycle tips to the left, resulting in a left turn, this occurs due to the principles of countersteering. Countersteering is a method used by cyclists and motorcyclists where a slight turn of the handlebars in one direction causes the bike to lean and steer in the opposite direction. The turning effect is a result of the conservation of angular momentum and the distribution of forces, particularly centripetal force, acting on the vehicle.
Leaning at the correct angle when making a turn on a bicycle is crucial. The ability to do this becomes instinctive and involves physics principles such as centripetal force and maintaining a line through the center of gravity for stability. The force exerted by the ground on the bicycle wheel can be decomposed into two perpendicular components; one balances the weight of the system and the other supplies the necessary centripetal force for turning.