Some one I know has a motorcycle, and he told me that it's much more difficult to drive than a car. Furthermore, in order to turn right, you push the right handlebar. Counterintuitive, huh? I was puzzling over this for about a month, trying to figure out how this was physically possible. After all, shouldn't the wheel turn to the left if you push right?
Well, I've finally got my answer! The wheel is precessing!
To visualize this, imagine that you are sitting on a motorcycle. The motorcycle must be moving very quickly, much faster than a bicycle. If it were moving at the same speed as a regular bike, then pushing right would indeed cause the wheel to turn left. But if the wheel is spinning very quickly, there will be too much energy invested in rotation for the wheel to simply turn like a bicycle's wheel.
The wheel of the motorcycle is spinning forward. This corresponds to an angular momentum going to your left. When you push on the right handle bar, you apply torque in the upwards direction. The angular momentum changes in the direction of the torque, tilting upwards. As a result, the entire spinning wheel will lean to the right. Thus, you turn right by pushing right.
Precession: not just for physics demonstrations!
Friday, May 2, 2008
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