Does friction always result in energy loss?

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Discussion Overview

The discussion revolves around the role of friction in the motion of a ball on a ramp, specifically addressing whether friction always results in energy loss and under what conditions it may be negligible or significant. The scope includes theoretical considerations of energy conservation, the effects of friction, and the conditions under which a ball may rotate or slide.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that if a ramp is frictionless, the ball would only slide without rotating, as there would be no force to induce rotation.
  • Others argue that if friction is present and allows the ball to rotate, it may lead to energy loss as the ball moves down the ramp, but this is contingent on whether the ball slides.
  • One participant suggests that mechanical energy is not necessarily lost if friction only facilitates rotation without sliding, indicating that the work done by friction could be zero in such cases.
  • Another viewpoint mentions that energy loss through friction can be negligible in certain scenarios, such as when a bowling ball rolls back up the ramp, but could be significant in cases with additional factors like sand on the ramp.
  • Air resistance is noted as another form of friction that is typically negligible unless extremely precise measurements are required.
  • A later reply humorously suggests that in a vacuum, the effects of air resistance would be irrelevant, indicating a consideration of ideal conditions for the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the implications of friction on energy loss, with some asserting that energy loss is not always present while others highlight conditions under which it could be significant. The discussion remains unresolved regarding the generality of these claims.

Contextual Notes

Participants acknowledge various conditions that could affect the role of friction, such as the presence of air resistance or surface materials like sand, which may influence energy loss but do not reach a consensus on the broader implications.

TheCanadian
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Hi,

If I have a ball at the top of a ramp, it will have rotational and translational kinetic energy as it begins moving. If the ramp was frictionless, just to confirm, would it be possible for the ball to rotate or would it just slide with the point of contact on the ramp fixed?

Also, if there is friction and the ball is allowed to rotate, will the ball lose energy while it goes from the top of the ramp to the bottom? To my understanding, friction is a nonconservative force and will result in energy dissipated from the system (i.e. the ball). But in this case, if friction is necessary for the ball to rotate, would I have to account for a loss of energy term when trying to figure out the ball's position, speed, and acceleration as it moves on the ramp? In this case, is the energy loss through friction negligible? Would it ever not be negligible?
 
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TheCanadian said:
Hi,

If I have a ball at the top of a ramp, it will have rotational and translational kinetic energy as it begins moving. If the ramp was frictionless, just to confirm, would it be possible for the ball to rotate or would it just slide with the point of contact on the ramp fixed? (1)

Also, if there is friction and the ball is allowed to rotate, will the ball lose energy while it goes from the top of the ramp to the bottom? (2)

To my understanding, friction is a nonconservative force and will result in energy dissipated from the system (i.e. the ball). (3)
But in this case, if friction is necessary for the ball to rotate, would I have to account for a loss of energy term when trying to figure out the ball's position, speed, and acceleration as it moves on the ramp? In this case, is the energy loss through friction negligible? (4)
Would it ever not be negligible? (5)

(1) Yes: slide. There is no force to make it rotate.
(2) not necessarily: if it doesn't slide at all the friction force does no work.
(3) mechanical energy is not lost if the friction force only makes the ball rotate (see (2) )
(4) can be safely ignored for e.g. a returning bowling ball that rolls up the ramp for the next shot.
(5) e.g. if there's a lot of sand on a ramp

--
 
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BvU is correct about the ramp, although there is another form of friction- air resistance. Again, it is very negligible, however you would account for it if you want EXTREMELY precise measurements.
 
Yeah, for a styrofoam ball in heavy fog this doesn't fly at all. So let's assume vacuum :smile:
 

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