# Conservation of angular momentum -- spinning a bicycle wheel in space

• I
In summary, the conservation of angular momentum is not violated in this scenario. The wheel and axle may initially slow down due to friction, but eventually they will reach a state of equilibrium and continue rotating forever, preserving angular momentum.
Suppose we have a rotating body like a bicycle wheel in space away from gravity. This body stops after a while due to friction between the wheel and wheel axles. Is not the conservation of angular momentum violated?

If it's just the wheel, then there's no axle exerting friction and the wheel will rotate without slowing forever. If it is mounted on a non-rotating bike, then the bike will take up the torque and begin rotating, conserving angular momentum.

nasu and PeroK
Suppose we have a rotating body like a bicycle wheel in space away from gravity. This body stops after a while due to friction between the wheel and wheel axles. Is not the conservation of angular momentum violated?
You are wrong to say that the body stops. As per @Halc's answer, the wheel slows and the axle spins up until both are rotating at the same rate. Then the wheel and axle continue to spin eternally, at rest with respect to each other.

nasu

## 1. What is conservation of angular momentum?

Conservation of angular momentum is a fundamental principle in physics that states that the total angular momentum of a system remains constant as long as there are no external torques acting on the system.

## 2. How does spinning a bicycle wheel in space demonstrate conservation of angular momentum?

When a bicycle wheel is spinning in space, it has an initial angular momentum. As there are no external torques acting on the wheel, its angular momentum remains constant. If the wheel is then reoriented, the direction of its angular momentum will change, but the magnitude will remain the same.

## 3. Why is conservation of angular momentum important?

Conservation of angular momentum is important because it is a fundamental law of nature that helps us understand and predict the behavior of rotating systems. It is also crucial for understanding the motion of objects in space, such as planets and galaxies.

## 4. Can conservation of angular momentum be violated?

No, conservation of angular momentum is a fundamental law of nature and cannot be violated. However, it may appear to be violated in certain situations due to external torques that are not initially accounted for.

## 5. How does conservation of angular momentum relate to the stability of a spinning bicycle wheel?

Conservation of angular momentum is directly related to the stability of a spinning bicycle wheel. As long as there are no external torques acting on the wheel, its angular momentum will remain constant and the wheel will continue to spin steadily. However, if external torques are applied, the wheel's angular momentum will change, causing it to wobble or fall over.

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