A spinning bicycle wheel balances like magic while dangling from a string. The spinning wheel also causes a student to spin on a rotating stool.

PHYS 3.4

The "Magic" Bicycle Wheel

This is probably the single most valuable physics demonstration one can do at a school. Suitable wheels can be purchased from various sources. The spinning seat is more expensive and difficult. Ours is portable with some effort.

Have students dangle the spinning wheel by a string and hold the spinning wheel in their hands to feel how difficult it is to tip it over.

 

About riding a bicycle

The "balancing" of a bicycle has traditionally been explained in terms of the angular momentum of the spinning wheel (the "gyroscope" effect). Some examples:

http://hyperphysics.phy-astr.gsu.edu/hbase/bike.html

http://science.nasa.gov/headlines/y2006/30nov_highorbit.htm (see the appendix under "more to the story").

http://www.physics.ucsb.edu/~circus/momentumdemo.htm

 

While this is certainly "standard physics", it turns out that it is also incomplete physics. It is possible to ride a bicycle that has counter rotating wheels and therefore no angular momentum. See for example http://www.people.cornell.edu/pages/aed29/Bad_Mechanics.htm and references included in that article. So, while the angular momentum will certainly affect the handling of the bicycle and allows the bicycle to travel upright with no rider, it does not actually play a key role in your balancing while riding a bicycle.

 

 

Watch the fingers in the wheel! Also, we recommend a sturdy, heavy spinning seat that has a seatbelt.