By admin on April 10th, 2012
Question by : What happens with a toy train on a bicycle wheel?
A toy train is initially at rest on a track fastened to a bicycle wheel, which is free to rotate.
1)How does the wheel respond when the train moves clockwise?
2)When the train backs up?
3)Does the angular momentum of the wheel-train system change during these maneuvers?
4)How would the resulting motions be affected if the train were much more massive than the track? Or vice versa?
Best answer:
Answer by electron1
A toy train is initially at rest on a track fastened to a bicycle wheel, which is free to rotate.
Momentum is ALWAYS conserved
For a rotating object, angular momentum is ALWAYS conserved
Angular momentum = moment of Inertia * angular velocity = I * ω
Total Initial angular momentum + Total final angular momentum = 0
I * ω (initial) + I * ω (final) = 0
I * ω (initial) = -1 * I * ω (final)
-1 times (I * ω) means in the opposite direction!!
Momentum of inertia has no direction, so, the direction of the final angular velocity must be the opposite of the initial angular velocity!!
Moment of Inertia is dependent on the mass of an object and the distance from the pivot point.
Answer to #4
If the wheel and track is more massive than the toy train, the angular velocity of the wheel will be less than the angular velocity of the track and bicycle wheel.
If the wheel and track is less massive than the toy train, the angular velocity of the wheel will be more than the angular velocity of the track and bicycle wheel.
1)How does the wheel respond when the train moves clockwise?
The more massive track and wheel moves counter clockwise at a lesser angular velocity than the less massive toy train is moving clockwise!!
2)When the train backs up?
The more massive track and wheel will rotate at a lesser angular velocity than the less massive toy train in the direction that causes the wheel to be moving forward in respect to the train.
3)Does the angular momentum of the wheel-train system change during these maneuvers? NO
For a rotating object, angular momentum is ALWAYS conserved
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