Heat with relation to work or energy

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Discussion Overview

The discussion revolves around the relationship between heat and energy in the context of collisions, specifically how to calculate the heat generated from the kinetic energy lost during such events. Participants explore the concepts of kinetic energy, potential energy, and the transformation of energy forms during collisions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant inquires about determining the heat released during a collision based on the force involved.
  • Another participant emphasizes that the macroscopic kinetic energy lost in the collision is more relevant than the force itself.
  • There is a suggestion that knowing the kinetic energy (KE) of the system could allow for the calculation of heat, contingent on the amount of KE lost.
  • It is noted that while energy can be lost in various forms, it may be reasonable to assume that most or all of the energy lost during a collision is converted to heat.
  • A participant proposes a method for estimating heat by calculating the initial potential energy (Ug) and kinetic energy (KE) just before impact, assuming that all lost energy is released as heat.
  • Another participant agrees that when an object comes to rest after falling, all mechanical energy is lost, with some energy potentially converted to sound or light, but ultimately all energy becomes random thermal motion.
  • It is suggested to set the initial potential energy equal to the heat for a good estimate of heat generated.

Areas of Agreement / Disagreement

Participants express varying views on the specifics of calculating heat from kinetic energy loss, with some agreement on the general approach but no consensus on the exact methods or assumptions involved.

Contextual Notes

Participants discuss different forms of energy loss and the assumptions made regarding the conversion of energy to heat, indicating potential limitations in their calculations and the need for careful consideration of energy transformations.

aglo6509
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Hello,
I know this seems silly to ask, but how could I figure out how much heat was given off when I know the force of an object hitting another?
 
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What's important is how much macroscopic kinetic energy is 'lost' in the collision, not the force involved.
 
So if I know the KE of the system I can find the heat?
 
aglo6509 said:
So if I know the KE of the system I can find the heat?
You need the amount of KE 'lost'. There are many kinds of energy other than 'heat' (random thermal energy), but you may be able to assume that most or all of the energy lost goes to 'heat'.
 
Doc Al said:
You need the amount of KE 'lost'. There are many kinds of energy other than 'heat' (random thermal energy), but you may be able to assume that most or all of the energy lost goes to 'heat'.

So if an object starts from rest 1/2 metre away from the object, I would first find Ug then KE right as it hits the object and assume all the lost energy is released as heat?
 
aglo6509 said:
So if an object starts from rest 1/2 metre away from the object, I would first find Ug then KE right as it hits the object and assume all the lost energy is released as heat?
If you drop something and it comes to rest, all the mechanical energy (PE + KE) is lost. Some might go to sound and light, but sooner or later it all becomes random thermal motion somewhere.

Just set the initial PE (measured from the final position) equal to the 'heat' for a good estimate.
 

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