Why is it quieter to lower your hand when you catch a falling ball?

Click For Summary

Discussion Overview

The discussion revolves around the phenomenon of sound production when catching a falling ball, specifically comparing the scenarios of catching it with a still hand versus lowering the hand during the catch. Participants explore the relationship between force, energy transfer, and sound energy in these different catching techniques.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that catching a ball with a still hand results in a loud noise due to a sudden stop, while lowering the hand results in a quieter catch because the change in momentum occurs over a longer time.
  • There is a question about the relationship between force and energy, with some participants expressing confusion about how energy can be conserved while sound energy is reduced in the second scenario.
  • One participant suggests that energy might be stored in the arm during the catch, likening it to a spring, and questions why it doesn't stretch back afterwards.
  • Another participant points out that controlling muscles to catch the ball consumes energy, raising questions about the energy dynamics involved in the catch.
  • It is mentioned that the kinetic energy of the ball is absorbed by the arm in both scenarios, but the energy required to apply to the arm is considered a biological factor rather than a physical one.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the energy dynamics and sound production in the two catching methods. There is no consensus on the specifics of energy transfer and sound generation, indicating ongoing debate and exploration of the topic.

Contextual Notes

Participants highlight the complexity of the relationship between force, energy, and sound, with some assumptions about energy transfer and biological factors remaining unresolved.

Alexander350
Messages
36
Reaction score
1
If there is a ball falling from a height due to gravity, and you keep your hand still and let the ball fall onto it, it stops suddenly and makes a loud noise. However, if you lower your hand as you catch the ball, like when a cricketer catches a fast moving ball, the catch is almost silent. I understand that in the second scenario, the force exerted is lower because the change in momentum of the ball occurs in a longer time. However, since there is the same amount of GPE being transferred during the collision, why does the second one have a lot less sound energy being released than the first?
 
Physics news on Phys.org
Alexander350 said:
However, since there is the same amount of GPE being transferred during the collision, why does the second one have a lot less sound energy being released than the first?

Alexander350 said:
I understand that in the second scenario, the force exerted is lower because the change in momentum of the ball occurs in a longer time

you answered your own question
what don't you like about that answer ?
 
  • Like
Likes   Reactions: russ_watters
What causes the release of sound energy? It kind of looks to me like you answered your own question when describing its background!
 
davenn said:
you answered your own question
what don't you like about that answer ?

russ_watters said:
What causes the release of sound energy? It kind of looks to me like you answered your own question when describing its background!

I can't seem to understand the relationship between the force and the energy. How can the second one have a lesser force and therefore less sound, but then the same amount of energy still get lost? Where does the energy go if it isn't sound or kinetic or GPE, and I can't imagine it being heat or anything else?
 
Alexander350 said:
I can't seem to understand the relationship between the force and the energy. How can the second one have a lesser force and therefore less sound, but then the same amount of energy still get lost? Where does the energy go if it isn't sound or kinetic or GPE, and I can't imagine it being heat or anything else?
You still answered that, though didn't go into the details:
...you lower your hand as you catch the ball...
 
russ_watters said:
You still answered that, though didn't go into the details:
Is it stored in your arm as if it were a spring, and if so, why doesn't it stretch back afterwards?
 
Alexander350 said:
Is it stored in your arm as if it were a spring, and if so, why doesn't it stretch back afterwards?
Well, kind of, but no; you don't let it. You have control over your muscles and making them do stuff consumes energy.
 
russ_watters said:
Well, kind of, but no; you don't let it. You have control over your muscles and making them do stuff consumes energy.
So isn't the energy used even more then... Why do you have to use energy to catch it but then less energy is released afterwards?
 
Alexander350 said:
So isn't the energy used even more then... Why do you have to use energy to catch it but then less energy is released afterwards?
All of the kinetic energy of the ball is absorbed by one thing or another (almost all by your arm) in both cases. How much energy you need to apply to your arm to make that happen is a matter of biology, not physics. It isn't actually clear to me which requires more.
 
  • #10
russ_watters said:
All of the kinetic energy of the ball is absorbed by one thing or another (almost all by your arm) in both cases. How much energy you need to apply to your arm to make that happen is a matter of biology, not physics. It isn't actually clear to me which requires more.
OK, so to sum up, the force when moving your hand down is lower which makes a quieter sound, but the work done in both situations is equal and the loss of kinetic energy into the arm is biology so not part of the problem. Thanks.
 

Similar threads

  • · Replies 53 ·
2
Replies
53
Views
5K
Replies
14
Views
3K
  • · Replies 4 ·
Replies
4
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 9 ·
Replies
9
Views
43K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 14 ·
Replies
14
Views
2K