Where Does Frictionless Energy Go?

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In summary, when the radius of the object is reduced, it spins faster due to the conservation of angular momentum.
  • #1
aviator
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i have a device where a spinning mass switches from a radius of 100 m to a radius of 1m by means of gearing, going the mass of 1 kg at a speed of 100 m/s

lets consider it frictionless

in order to reduce the radius i have to aply a work, the energy to aply that work comes from the 100 m/s of the mass because there's no other energy in the system

so when the ball has a radius of 1 m it has a lower speed having lost kinetic energy

my question is if the device is frictionles where has this kinetic energy gone to?
 
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  • #2
I`m not sure what you mean exactly, but when you reduce the radius of the spinning object it will start to spin faster (conservation of angular momentum), so it picks up rotational kinetic energy (equal to the work you performed to bring the mass closer to the axis of rotation).
 
  • #3
a ball is geared to an axe in such way that the radius decreases constantly as it spins

would it be correct to say that because of conservation of momentum if when it has a radius of 100 m has a speed of 100m/s when it has a radius of 1 m still has a speed of 100 m/s?
 
  • #4
No, since the initial angular momentum is rmv=(100)(1)(100) = 10.000 kg m^2/s, when the ball

spins with a radius of 1m, the angular momentum will be still be 10.000 kgm^2/s =(1)(1)(v). So v=10.000 m/s.

If you pull in the ball radially, the torque on the ball will be zero, so its angular momentum is conserved.
Linear momentum obviously is not, since the ball rotates (there's a centripetal force acting on it).
 
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  • #5
you are wrong its been accepted by a mod here that speed is kept at 100 m/s however radius, this case is called a tetherball
 
  • #6
aviator said:
you are wrong its been accepted by a mod here that speed is kept at 100 m/s however radius, this case is called a tetherball
As usual, you have no idea what you are talking about. You must specify whether you are actively reeling in the cable (this is what Galileo assumed in his response to your vaguely worded question) or just letting it wrap around a pole (like the tetherball case). These are different scenarios with different answers.

Stick to one scenario and get it straight. Stop posting the same thing over and over.
 

1. What is frictionless energy?

Frictionless energy refers to the energy that is not lost due to frictional forces. It is the total amount of energy that can be harnessed from a system without any loss due to friction.

2. Where does frictionless energy go?

Frictionless energy does not go anywhere. It remains within the system and can be harnessed for useful work. Unlike frictional energy, which is lost as heat, frictionless energy is conserved within the system.

3. How is frictionless energy different from other forms of energy?

Frictionless energy is different from other forms of energy because it is not lost due to frictional forces. Other forms of energy, such as kinetic energy or potential energy, can be converted into frictional energy and lost due to friction.

4. Can frictionless energy be harnessed for practical use?

Yes, frictionless energy can be harnessed for practical use. In fact, many machines and devices are designed to minimize friction and utilize the maximum amount of frictionless energy. This helps to increase efficiency and reduce energy loss.

5. How can we reduce the loss of energy due to friction?

The loss of energy due to friction can be reduced by using lubricants, designing smoother surfaces, and minimizing contact between surfaces. Additionally, using materials with lower coefficients of friction can also help to reduce energy loss due to friction.

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