What will happen to the rotational motion

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Discussion Overview

The discussion revolves around the effects of a collision on the rotational motion of a body that is rotating and moving towards a wall. Participants explore the implications of different conditions such as friction and elasticity on both translational and rotational motion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that upon colliding with a wall, the direction of motion will reverse, but questions what will happen to the rotational motion under the assumption of infinitely rough conditions.
  • Another participant argues that if there is no friction and the collision is perfectly elastic, the body would return in the opposite direction with the same spin. However, they note that with friction, the body would not go straight back and its rotation would slow down depending on the frictional force.
  • A different participant states that the translational motion will reverse in a perfectly elastic collision, while the rotational motion will change based on the wall's friction. They mention a range of possible outcomes for the rotational change, from slight slowing to a complete reversal of spin under ideal conditions.
  • Another contribution emphasizes that for the rotational motion to stop, the wall must impart an angular impulse equal and opposite to the ball's spin, which is considered idealistic and not physically replicable.

Areas of Agreement / Disagreement

Participants express differing views on the effects of friction and elasticity on rotational motion, indicating that multiple competing perspectives exist without a clear consensus on the outcomes of the collision.

Contextual Notes

Participants acknowledge that ideal conditions are necessary for certain outcomes, such as reversing rotational motion completely, but these conditions may not be physically achievable. There are also mentions of assumptions that may not have been fully articulated.

nishant
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if a body is rotating forward towards a wall,colides with the wall ofcourse the direction of motion will be reversed,,but what will happen to the rotational motion,if it is given that the infinitely rough
 
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Did you stop in the middle of a sentence? Acutally "of course the direction of motion will be reversed" is not "of course" at all. If there is no friction (and the collision is perfectly elastic) then the body would go back in exactly the opposite direction with exactly the same spin. If there is friction however (I don't think it needs to be "infinitely rough"!) The ball exerts some force on the wall in one direction and so will not go straight back but slightly of to one side while its rotation slows slightly. What "slightly" is depends upon the friction.
 
The translational motion (not rotation) will be reverse if the wall is perfectly elastic and will not fail upon impact. The rotation will change depending on the friction of the wall. The range of rotational change will be from a rotation that is slightly slowing down to a rotation of opposite spin with the same magnitude. The same magnitude requires ideal conditions which you can figure out because I will probably leave some assumptions out. Can someone list all the ideal conditions for the translational and rotational motion to be reversed upon impact of the wall?
 
Translational motion is conserved in a perfectly elastic frictionless collision.
Rotational is another thing though. For the rotational to be stopped, the wall would need to impart an angular impulse such that its magnitude is exactly that of the spinning ball (and opposite direction). If this is done in an infinitely small time period (to maintain the elastic requirement) the ball will lose all its rotational motion. An example is if you threw it at something like a conveyor belt. To reverse the motion with the same magnitude, your angular impulse would need to be twice as strong as the initial angular momentum of the ball.

Ofcourse these are idealistic, and not physically possible to replicate.
 

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