Understanding Hammerthrow Forces, (no friction with ground)

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Discussion Overview

The discussion centers around the forces involved in the hammer throw, particularly focusing on the implications of performing the throw without friction with the ground. Participants explore the mechanics of rotation and angular momentum in the context of an athlete attempting to throw a heavier ball while airborne.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that during the hammer throw, the athlete generates centripetal force on the ball, while the ball exerts a reactionary centrifugal force on the athlete.
  • One participant questions the feasibility of an athlete throwing a heavier ball than themselves while in the air, suggesting that the athlete might rotate around the ball instead.
  • Another participant emphasizes that friction is necessary for the athlete to spin the ball around themselves, arguing that without it, spinning is not possible.
  • Some participants discuss the ability to rotate in midair by using body movements, noting that while translation is not possible without a surface to push against, rotation can occur through limb movement.
  • A later reply clarifies that if a person uses their limbs to rotate, they can throw the hammer, but they would move in the opposite direction due to conservation of angular momentum.
  • Participants express differing views on whether the scenario described aligns with the actual mechanics of the hammer throw, with some asserting it diverges from traditional techniques.

Areas of Agreement / Disagreement

Participants generally disagree on the mechanics of throwing a hammer without ground friction, with multiple competing views on the feasibility and implications of such a scenario. The discussion remains unresolved regarding the specific mechanics involved.

Contextual Notes

Limitations include assumptions about the absence of friction and the implications for angular momentum, as well as the potential misunderstanding of the original scenario posed by the thread starter.

ultrauser
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If I understand it correct during hammerthrow an athlete muscles cause Fcentripetal force on a ball and ball cause reaction Fcentrifual force on athlete.
The athlete also cause Frotation on ball by rotating his body and ball cause Freaction on athlete.

What would happen if athlete would try to throw the heavier ball than himself being in the air - by rotating his body (no friction between athlete and the Earth - I mean the athlete and the ball are both in the air) ? Would it be even possible or would athlete rotate himself around ball(cause ball is heavier) ?
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Hint: One of the basics of the hammer throw event is for the athlete to keep both feet in contact with the ground for as much time as possible. If you see a hammer throw in slow motion, notice how quick they are to put their feet back on the ground in the moments where they have to lift one of them.
 
Friction on the ground (or something) is required in order for the athlete to spin the ball around himself. With no friction the athlete cannot even spin himself around.
 
Drakkith said:
With no friction the athlete cannot even spin himself around.
I can spin myself around in the air when I jump
 
ultrauser said:
I can spin myself around in the air when I jump

Sure, by pushing off the ground in a certain way. If I place you into zero g and you have nothing to push off of, you will not be able to turn around.
 
Drakkith said:
Sure, by pushing off the ground in a certain way. If I place you into zero g and you have nothing to push off of, you will not be able to turn around.
Translation is not be possible, but rotation is possible because a person can rotate / swivel their arms and/or legs, and since the total angular momentum remains zero, the persons body rotates / swivels in the opposite direction. Once the person stops moving their arms and/or legs they will end up facing in a new direction (but no translation has occurred). If this method were used with a hammer, then the hammer could be released and thrown, but the person would end up traveling in the opposite direction (and with opposing angular momentum), and the center of mass of person and hammer would not move.
 
rcgldr said:
Translation is not be possible, but rotation is possible because a person can rotate / swivel their arms and/or legs, and since the total angular momentum remains zero, the persons body rotates / swivels in the opposite direction. Once the person stops moving their arms and/or legs they will end up facing in a new direction (but no translation has occurred). If this method were used with a hammer, then the hammer could be released and thrown, but the person would end up traveling in the opposite direction (and with opposing angular momentum), and the center of mass of person and hammer would not move.

Of course, but I don't consider this to be anything like what the OP was imagining in their original post with the athlete swinging the ball around themselves in midair. Unless I misunderstood the question.
 
Drakkith said:
Of course, but I don't consider this to be anything like what the OP was imagining in their original post with the athlete swinging the ball around themselves in midair.
But that's the situation I had in mind. The person in midair, pushes the ball away from themselves, then starts swinging the ball in a circle while the persons body would rotate in the opposite direction. Swiveling of the legs could be used to reduce the person's rate of rotation and increase the hammer's rate of rotation. The person then releases the hammer and they both move away from each other, while the center of mass of person and hammer remains motionless, and angular momentum of person and hammer remains at zero.
 
Last edited:
Okay, I can see that working. I was imagining both the athlete and the ball rotating with each other, which isn't possible given conservation of angular momentum.
 
  • #10
It will work to get the ball away, yes. Unfortunately, it is also quite unrelated to how the hammer throw event is performed where the thrower is actually rotating along with the hammer.
 
  • #11
Drakkith said:
Sure, by pushing off the ground in a certain way. If I place you into zero g and you have nothing to push off of, you will not be able to turn around.

Not on-topic for this thread, but even with zero angular momentum throughout the exercise, one can contort and uncontort the body and thereby change orientation.
 
  • #12
jbriggs444 said:
Not on-topic for this thread, but even with zero angular momentum throughout the exercise, one can contort and uncontort the body and thereby change orientation.
It's how a cat can be dropped a short distance while initially paws up and manage to rotate it's body by swiveling about it's mid section so that it lands paws down.
 

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