http://www.physlink.com/Education/askExperts/ae288.cfm
The reason that you stay up on a bike is that angular momentum, like regular momentum, must be conserved if no external torques act on the object. Because angular momentum is a vector, not only must its magnitude be conserved, but also its direction. This implies that any change in the orientation of the object will change the vector for angular momentum. Therefore, tops stay up because the angular momentum wants to stay conserved in the same direction.
Paragraph with Ellipsis
The reason that you stay up on a bike is that angular momentum, like regular momentum, must be conserved if no external torques act on the object. Because angular momentum is a vector, not only must its magnitude be conserved, but also its direction. This implies that any change in the orientation of the object will change the vector for angular momentum. Therefore, [the bike will] stay up because the angular momentum wants to stay conserved in the same direction.
Paraphrase
A bike wants to stay up at speed because of gyroscopic forces or also known as angular momentum. If a person would hold a bicycle wheel on a axle in their hands a had someone spin the wheel they would feel the forces acting on the spinning wheel. The person would notice that there where no forces felt until the wheel is turned left, right or leaned. What this person is feeling are the gyroscopic forces. The wheel wants to stay in the upright position and when the wheel is leaned or turned the person is feeling the wheel trying to return to its straight ahead position. The straight ahead position is where the three forces acting on the spinning wheel are equalized.
Summary
A bike stays up because of the laws of angular momentum. Angular momentum is a vector and because of this the object's magnitude and its direction must be conserved. This means that any change in the object's manitude or direction will change the angular momentum vector. The reason the tire stays up is because angular momentum vector wants to equalize.
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Brian, I think your paraphrase and summary really good; your paragraph with elipses, though, doesn't have elipses. You used the brackets well, but perhaps you could have said something like:
ReplyDeleteThe reason that you stay up on a bike is that angular momentum. . . must be conserved
Good job though!