Kinetic energy question. (layman)

Click For Summary

Discussion Overview

The discussion revolves around the concept of kinetic energy, particularly in relation to motion and reference frames. Participants explore how kinetic energy is perceived differently depending on the observer's frame of reference, as well as the implications of relative motion on the kinetic energy of objects.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that if motion is relative, then both the ball and the hand throwing it possess kinetic energy.
  • Others argue that kinetic energy is a property of anything in motion, leading to confusion about how it applies when the observer is also in motion.
  • One participant questions whether an object has different kinetic energy in different frames of reference, suggesting that the total energy of an object may not be absolute.
  • Another participant clarifies that the kinetic energy of an object can appear different depending on the observer's motion relative to the object.
  • Some participants discuss the implications of throwing a ball at different speeds relative to a moving observer, noting that the perceived impact can vary based on the observer's state of motion.

Areas of Agreement / Disagreement

Participants express confusion and uncertainty regarding the relationship between kinetic energy and relative motion. There is no consensus on how kinetic energy should be understood in different reference frames, and multiple competing views remain evident throughout the discussion.

Contextual Notes

Participants highlight limitations in understanding kinetic energy due to the dependence on the observer's frame of reference, and there are unresolved questions about how kinetic energy is measured and perceived.

Moris526
Messages
16
Reaction score
0
Hi all.
English is not my native language, so bare with me (joke i found googling the right word). I am from Argentina.
My question.

If i throw a ball, i have learned it has kinetic energy. But if motion is relative doesn't that mean that my hand has the kinetic energy too?

thanks.
 
Last edited:
Physics news on Phys.org
Moris526 said:
But if motion is relative doesn't that mean that my has the kinetic energy too?
Yes.
 
Moris526 said:
doesnt that mean that my has the kinetic energy too?

I think you omitted a word in the area that I put in boldface. My (your) what has?
 
Sorry. Yes, I omitted the word ¨HAND¨.
 
Kinetic energy is a property of anything in motion. The term kinetic means motion.
 
CAB12 said:
Kinetic energy is a property of anything in motion. The term kinetic means motion.

I don't get it. If anything in motion has kinetic energy and motion is relative then the kinetic motion of an abject is relative? if an object passes me by it has kinetic energy but if i move with it, it does not?

Confused here!.
 
Moris526 said:
I don't get it. If anything in motion has kinetic energy and motion is relative then the kinetic motion of an abject is relative?
Yes.
 
Moris526 said:
I don't get it. If anything in motion has kinetic energy and motion is relative then the kinetic motion of an abject is relative? if an object passes me by it has kinetic energy but if i move with it, it does not?

Confused here!.

Hand has kinetic energy ball does not, it isn't moving. Only thing the ball has is internal energy.

Ball thrown, thus has kinetic energy. What matters here is the direction you are throwing it, up, down, left, or right? That would be the reference frame.

Relative motion = you on a plane moving.
 
  • #10
Just to be clear: you are talking about after the ball was thrown, right? Or do you mean while throwing the ball?
 
  • #11
CompuChip said:
Just to be clear: you are talking about after the ball was thrown, right? Or do you mean while throwing the ball?

Yes, after.
 
  • #12
Wikipedia " In physics, the kinetic energy of an object is the energy which it possesses due to its motion.[1] It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity"

Where is the kinetic energy? If it is in the object and comes from an acceleration, that is in relation to a frame of reference, right?. So the object has a diferent kinetic energy in diferent frames of reference? Or it has kinetic energy from a frame of reference?
 
  • #13
Moris526 said:
I don't get it. If anything in motion has kinetic energy and motion is relative then the kinetic motion of an abject is relative? if an object passes me by it has kinetic energy but if i move with it, it does not?

Confused here!.

That is in part correct. Relative to you running it has less kinetic energy than if you were standing still, that is: If I throw a ball at you at 10m/s and it hits you while you're standing still, then I throw the same ball at you at the same speed, but this time you are running away at 5m/s. The ball has the same amount of kinetic energy in both instances, but getting hit with the ball in case one will hurt more than getting hit by the ball in case 2.
 
  • #14
Jesse H. said:
That is in part correct. Relative to you running it has less kinetic energy than if you were standing still, that is: If I throw a ball at you at 10m/s and it hits you while you're standing still, then I throw the same ball at you at the same speed, but this time you are running away at 5m/s. The ball has the same amount of kinetic energy in both instances, but getting hit with the ball in case one will hurt more than getting hit by the ball in case 2.

If i measure the energy of the ball as it is approaching me, don't i get different ones? If this is true, the total energy of an object is not absolute?
 
  • #15
Moris526 said:
If i measure the energy of the ball as it is approaching me, don't i get different ones? If this is true, the total energy of an object is not absolute?

Exactly. It is relative.
 

Similar threads

  • · Replies 41 ·
2
Replies
41
Views
4K
  • · Replies 21 ·
Replies
21
Views
2K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 40 ·
2
Replies
40
Views
5K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 138 ·
5
Replies
138
Views
9K
  • · Replies 9 ·
Replies
9
Views
2K