Even a little first-grader can stay up on a bicycle if he can get his bicycle moving fast enough because
A) the angular momentum of the wheels wants to stay horizontal, due to conservation of angular momentum.
B) the first-grader's weight causes a torque too small to make the bicycle fall sideways when moving.
C) pedaling faster is easier once you are stable, and more pedaling increases net angular momentum.
D) All of these.

Question

Quizplus · Accepted Answer

All three options play a role in allowing the first-grader to stay up on the bicycle. First, the angular momentum of the wheels wants to stay horizontal due to conservation of angular momentum, which helps keep the bicycle stable. Second, the first-grader's weight causes a torque too small to make the bicycle fall sideways when in motion. Finally, once the first-grader is stable, pedaling faster is easier, which results in an increase in net angular momentum.

Even a Little First-Grader Can Stay Up on a Bicycle