Drop a ball - where does the energy go?

In summary, in the conversation, the participants discuss the concept of potential energy and where it goes when an object is dropped. They also mention the different forms of energy, such as heat and kinetic energy, and how they can be transformed into one another. Additionally, the possibility of using paper and alcohol to start a fire is brought up, with some skepticism about its effectiveness due to the quick dissipation of heat. Finally, the idea of plastic deformation and its energy transformation is mentioned.
  • #1
oneamp
219
0
Hi -

If I lift a bowling ball in the air, so that it has potential energy, then drop it on the dirt, it makes a sound and a dent. Where did all the energy go? It did not all go to sound, since there's a dent, right? A small bit went to heat... what else?

Thanks
 
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  • #2
oneamp said:
A small bit went to heat...
All of it goes to heat, after a while.
 
  • #3
The bit that went to heat aint small. Do the following experiment. Ask someone to hold a piece of paper up in the air for you and Bang two pieces of steel together making sure the paper is caught in between them. There should be a burnt spot on the paper afterwards.
 
  • #4
Thanks
 
  • #5
That's interesting, dauto. If I'm lost in Alaska and about to freeze, and find two hammers and some paper, is it possible that I could start a fire to save my life?
 
  • #6
oneamp said:
Hi -

If I lift a bowling ball in the air, so that it has potential energy, then drop it on the dirt, it makes a sound and a dent. Where did all the energy go? It did not all go to sound, since there's a dent, right? A small bit went to heat... what else?

Thanks
Initially some energy goes into the kinetic energy of the little pieces of dirt that are moved away to make that 'dent'. Of course, all of those eventually (very quickly) stop because of friction- which is the same as saying the energy becomes heat energy. (In the long scale 'eventually' all energy becomes heat.)
 
  • #7
Oldfart said:
That's interesting, dauto. If I'm lost in Alaska and about to freeze, and find two hammers and some paper, is it possible that I could start a fire to save my life?

Unlikely. The paper burns but you don't get a flame that way. The heat dissipates to quickly
 
  • #8
dauto said:
Unlikely. The paper burns but you don't get a flame that way. The heat dissipates to quickly

Hmmm... What if you lightly soaked the paper in alcohol first? Anyone want to give that a try?
 
  • #9
Oldfart said:
Hmmm... What if you lightly soaked the paper in alcohol first? Anyone want to give that a try?

Nah, you do it ... I'm drinking my alcohol :smile:
 
  • #10
Oldfart said:
Hmmm... What if you lightly soaked the paper in alcohol first? Anyone want to give that a try?

As mentioned by dauto the heat dissipates very fast, I don't think alcohol will be effective since the temperature will go below the flash point even before oxygen is supplied.
 
  • #11
Well, we won't really know until some idiot tries it, right?

Maybe I'll give it a shot tomorrow...
 
  • #12
Heat is not the only energy transformation. The dent means plastic deformation, so the breaking or tensing material. So energy gets stored in material induced stresses and get's absorbed by the breaking of chemical or physical bonds. The plastic deformation energy is not all transformable to heat and is very material dependent.
 

1. Where does the energy go when a ball is dropped?

When a ball is dropped, the potential energy stored in the ball due to its position above the ground is converted into kinetic energy as it falls. The kinetic energy is then converted into other forms of energy, such as sound and heat, upon impact with the ground or other objects.

2. Does energy disappear when a ball is dropped?

No, energy cannot be created or destroyed, it can only be converted from one form to another. Therefore, the energy from a dropped ball does not disappear, it is simply transformed into different forms.

3. Why does a ball bounce when dropped?

When a ball hits the ground, some of its kinetic energy is transferred to the ground and converted into sound and heat. The remaining kinetic energy causes the ball to compress and deform, storing potential energy. This potential energy then converts back into kinetic energy, causing the ball to bounce back up.

4. What happens if a ball is dropped in a vacuum?

In a vacuum, there is no air resistance to slow down the ball's fall. Therefore, the ball will continue to accelerate until it reaches the maximum possible speed, known as terminal velocity. When the ball hits the ground, all of its kinetic energy is converted into potential energy, causing it to bounce up to the same height.

5. Can the energy from a dropped ball be harnessed?

Yes, the energy from a dropped ball can be harnessed using mechanisms like a pulley system or a spring. These mechanisms can capture and store the energy from the ball's fall, which can then be used to do work, such as lifting an object or powering a machine.

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