# Is the Spinning Wheel's Rotation Maintained? | Investigating Kinetic Energy

• SpaceThoughts
In summary: You should be able to work out how much work is done by or on the hands.In what way? The setup is quite simple ... two springs stretched, and a wheel with kinetic energy. You should be able to work out how much work is done by or on the hands.
SpaceThoughts
Hi.

I searched and found no answer to this simple question:
Is the spinning wheel in this videoclip keeping the same rotation (kinetic energy) when flipped upside down and back again?

SpaceThoughts said:
If the bearings are friction-less they have no means to apply any torque along the spin axis. So if there is also no drag on the rest of the wheel, it will maintain its kinetic energy.

In the movie it's correctly explained with conservation of angular momentum. When turning the wheel upside down the guy has to so work which gets converted in the additional energy to make him and the wheel rotate as a whole, keeping angular momentum constant.

I’ve been thinking a lot about the experiment done in the video above, and to me it seems we are losing energy every time we recycle the experiment, questioning conservation of energy.

Think of the laboratorium as an empty isolated system only containing what we need to make the experiment.
Imagine the guy in the video is a robot, that gets the energy for the experiment from two separate stretched springs in his body.

The robot performs two actions during the experiment:
1. Turning the wheel upside down, using the potential energy from the first spring to perform this action.
2. Turning the wheel back again to its original position, using the potential energy of the second spring to perform this action.

The total energy in the system before the two action starts, is the kinetic energy of the spinning wheel, and the two times potential energy of the springs.
At the end of the experiment, the spinning wheel has the same kinetic energy, but the potential energy of the two springs are missing.

Every time we want to repeat this experiment, we would need to stretch the two springs again, converting energy to potential energy in the springs, that we won’t get back.

SpaceThoughts said:
I’ve been thinking a lot about the experiment done in the video above, and to me it seems we are losing energy every time we recycle the experiment, questioning conservation of energy.
Rest assured, energy will be conserved. You should depend on that to form the next logical question --- where does the energy go?

anorlunda said:
Rest assured, energy will be conserved. You should depend on that to form the next logical question --- where does the energy go?
That is what I am asking here. There seems to be no heat loss. Comparing the start scenario with the end scenario shows a difference.

SpaceThoughts said:
That is what I am asking here. There seems to be no heat loss. Comparing the start scenario with the end scenario shows a difference.
What about the hands of the man? Work done by or on the hands. Have you accounted for that?

SpaceThoughts
SpaceThoughts said:
The robot performs two actions during the experiment:
1. Turning the wheel upside down, using the potential energy from the first spring to perform this action.
2. Turning the wheel back again to its original position, using the potential energy of the second spring to
This is way to vague to analyse energy and work done.

anorlunda said:
What about the hands of the man? Work done by or on the hands. Have you accounted for that?

Nice expression, and thanks for spending your time on me:-)
Yes, I should say work done by the hands in both cases. Force is used in both flipping the wheel upside down and back. If we started the experiment with the wheel upside down, it would be the same cycle, only the direction of the guy/robot tuning around would be opposite. Where is the trace of the energy used? If there were considerable heatloss because of friction, the guy/robot should not be able to stop himself completely from turning in the end of the cycle. Are you saying between the lines, that the energy goes to making energy disappear? The netto result of that must be loss of energy. From looking at the isolated system from the outside.

A.T. said:
This is way to vague to analyse energy and work done.
In what way? The setup is quite simple ...

## 1. How does the spinning wheel maintain its rotation?

The spinning wheel maintains its rotation through the conservation of angular momentum. This means that the wheel will continue to spin at a constant rate unless acted upon by an external force.

## 2. What is kinetic energy and how is it related to the spinning wheel's rotation?

Kinetic energy is the energy an object possesses due to its motion. In the case of the spinning wheel, its rotation creates kinetic energy. The faster the wheel spins, the more kinetic energy it has.

## 3. What factors affect the maintenance of the spinning wheel's rotation?

The maintenance of the spinning wheel's rotation is affected by several factors, including the initial force used to spin the wheel, the mass and shape of the wheel, and any external forces acting upon the wheel, such as friction or air resistance.

## 4. Can the spinning wheel's rotation ever stop?

In theory, the spinning wheel's rotation will continue indefinitely due to the conservation of angular momentum. However, in reality, external forces such as friction and air resistance can slow down and eventually stop the wheel's rotation.

## 5. How is the spinning wheel's rotation important in understanding other scientific concepts?

The spinning wheel's rotation is an important concept in physics and is used to explain other phenomena, such as the movement of planets, gyroscopic stability, and the behavior of spinning tops. It also helps us understand the relationship between energy, motion, and forces.

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