Final answer:
Bike crashes most commonly occur when cyclists are not seen during vehicle maneuvers, such as left turns. Physics explains this through concepts like countersteering, which cause motorcycles to lean and turn in the opposite direction of the handlebar input.
Step-by-step explanation:
Bike crashes are most common when drivers do not see the cyclist, especially during turns or when external forces are applied unexpectedly, such as a hit from a vehicle. In the scenario described, a driver making a left turn did not see the cyclist, leading to a collision. Similarly, understanding vehicle dynamics is crucial for preventing accidents; for instance, motorcycle handling can be explained by physics.
When the physics student pulls back lightly on the right handlebar, the motorcycle tips to the left due to countersteering. This initiates a left turn because the action of pulling back on the handlebar actually causes the front wheel to turn slightly to the right, which results in the bike leaning and turning to the left due to angular momentum and the conservation of gyroscopic forces.