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When we released a bouncing object in a vacuum chamber, the object will fall, contact the ground of the chamber and bounce back up. We know that the object will not return to its original height because energy is not conserved and lost when the object struck the ground.

In high school, we learned that the vacuum chamber could not conserved the bouncing object's energy totally and hence, some of it's potential energy was lost to heat and sound when it struck the ground.

I am curious why would the bouncing object loses it's energy in the form of heat and sound only and does not lose it's energy in other forms of the EM's spectrums such as radio wave, micro wave, visible light wave, ultraviolet wave, x-ray wave and gamma wave?

Thanks.

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3 Answers 3

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If you take a rubber ball and drop it, the rubber polymer molecules flex back and forth and stick & slide past one another as the ball deforms. This deformation generates heat by internal friction. But there are no physical mechanisms or processes involved in deforming a piece of rubber which are capable of generating any of the EM wavelengths you mention.

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Mechanical kinetic and potential energy of the ball is not conserved but total energy is. The inelastic collision of the ball with the ground converts some of the macroscopic mechanical kinetic energy into an increase in microscopic molecular kinetic energy due to internal friction.

The increased molecular activity does two things: (1) It increases the temperature of the ball resulting in heat transfer to the cooler surroundings and (2) It causes vibrations of materials (solids, liquids and gases) in contact with the vibrating molecules at the surface of the ball producing sound. Of course in the vacuum jar there is no air to be heated or that can carry sound waves. But the ground can be heated by conduction and can be a medium for carrying sound waves.

EM waves are produced by oscillating (vibrating) electric charge. It is applicable here for heat transfer by infrared (thermal) radiation, but not the EM wavelengths you’re listed.

Hope this helps

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Even in a vacuum the ball is radiating a small amount of energy in the EM spectrum by emitting infra-red radiation. However, the kinetic energy of the ball is so large that the energy emitted as EM radiation is negligible in comparison. For EM radiation to have a measurable impact on the motion of the ball, you would either have to make the ball very hot or very small.

Another way in which an object can "lose" energy in a vacuum is by creating gravitational waves. For the bouncing ball this is again negligible, but for massive objects moving very quickly (e.g. the components of a binary pulsar) it can have a measurable effect.

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