Inelastic crash

  • Thread starter bobie
  • Start date
  • #26
NTW
302
26
I never said that, did I? and that's why I said I am wearing a baseball catcher's glove. The energy goes 99% to my poor hand. Sure
In this case the ball is douing no work on the ball. And I am doing negative work on the ball.
3) has no answer yet, can you tell me a case when I stop the ball with my hand doing no (or less) work?

Thanks a lot

In the first case, that of the glove, lets suppose that your hand doesn't move at all. Well, the KE of the ball will transform in work done by the glove and your hand tissues, resisting the braking ball and deforming elastically. The ball will also deform elastically, and if it does not rebound, when the deformations disappear and everything regains its former shape, all the KE the ball had will have turned into heat, rising the temperature of the glove, the hand, the ball, and the surrounding air...

If your hand were indeformable, and didn't move at all when struck by the ball, all the elastic deformations mentioned above will take place in the ball only...
 
  • Like
Likes bobie
  • #27
bobie
Gold Member
720
2
In the first case, that of the glove, lets suppose that your hand doesn't move at all. Well, the KE of the ball will transform in work done by the glove and your hand tissues, resisting the braking ball and deforming elastically. The ball will also deform elastically, and if it does not rebound, when the deformations disappear and everything regains its former shape, all the KE the ball had will have turned into heat, rising the temperature of the glove, the hand, the ball, and the surrounding air...

If your hand were indeformable, and didn't move at all when struck by the ball, all the elastic deformations mentioned above will take place in the ball only...
Ok i know all that, but all in all I suppose my hand (and glove) are still doing 95% of the work and it it is a stone even 99. When can I do zero work?
 
  • #28
NTW
302
26
Ok i know all that, but all in all I suppose my hand (and glove) are still doing 95% of the work and it it is a stone even 99. When can I do zero work?

I'm not sure of that 95%, but all the KE will go into the ball, in other energy form, and possibly ending up in heat, if you have a fully indeformable and immobile hand and glove...
 
  • #29
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
36,736
7,082
So, I have learned that if I want to stop a ball (E = k) I must spend k J of energy doing work in the direction opposite to its v:
I hold up my hand and stop it . I have done negative work on the ball and spent k J
No, if you have done negative work then you have not spent k J, you have absorbed k J. The ball does k J, you do -k J (i.e. absorb k J), and the total work done is 0 (which is correct).
 
  • #30
Nugatory
Mentor
13,498
6,604
I do not have a specific question, if you have, I'd appreciate it. I just want to know in general:
A thread that starts this way isn't going to respond well the homework help process, and this one is no exception.
 

Related Threads on Inelastic crash

  • Last Post
Replies
1
Views
2K
Replies
1
Views
10K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
8
Views
991
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
0
Views
1K
  • Last Post
Replies
9
Views
1K
  • Last Post
Replies
8
Views
2K
  • Last Post
Replies
3
Views
3K
Replies
2
Views
3K
Top