If Heat Is Motion, Why Isn’t All Motion Heat?

[sol_2001]

Homework Statement

If heat is merely molecular motion, what is the difference between a hot, stationary baseball and a cool, rapidly moving one?

Relevant Equations

No relevant equations as it is a conceptual question.

This is from the Exercises for the Feynman Lectures on Physics, Exercise 1.1. I believe that a hot stationary ball has more thermal energy due to the inter-molecular motion within the baseball, whereas a cool, fast-moving baseball has more kinetic energy due to the motion of the whole macroscopic object in a particular direction. Is that correct?

 

[haruspex]

Homework Statement: If heat is merely molecular motion, what is the difference between a hot, stationary baseball and a cool, rapidly moving one?
Relevant Equations: No relevant equations as it is a conceptual question.

This is from the Exercises for the Feynman Lectures on Physics, Exercise 1.1. I believe that a hot stationary ball has more thermal energy due to the inter-molecular motion within the baseball, whereas a cool, fast-moving baseball has more kinetic energy due to the motion of the whole macroscopic object in a particular direction. Is that correct?

Is that the exact wording of the question? I ask because in scientific usage "heat" only refers to the transfer of energy between bodies. Molecular motion within a body is "internal thermal energy". See e.g. https://en.wikipedia.org/wiki/Thermal_energy.
If that is the wording, your answer looks good enough.

It is interesting to consider intermediate scenarios. What about a system consisting of two balls orbiting each other? Two million balls? https://en.wikipedia.org/wiki/Maxwell's_demon

 

[Gavran]

Homework Statement: If heat is merely molecular motion, what is the difference between a hot, stationary baseball and a cool, rapidly moving one?
Relevant Equations: No relevant equations as it is a conceptual question.

This is from the Exercises for the Feynman Lectures on Physics, Exercise 1.1. I believe that a hot stationary ball has more thermal energy due to the inter-molecular motion within the baseball, whereas a cool, fast-moving baseball has more kinetic energy due to the motion of the whole macroscopic object in a particular direction. Is that correct?

You ask about the difference between thermal energy and mechanical energy. Both are two different forms of kinetic energy, which is the energy of motion. All types of kinetic energy can be categorized as radiant energy, thermal energy, sound energy, electrical energy, and mechanical energy; therefore, thermal energy does not cover all forms of kinetic energy.
Mechanical energy is sometimes called “motion energy,” and this is the main reason for misunderstanding because, in this case, “motion energy,” as the other name for mechanical energy, does not capture every type of energy of motion.

 

[sol_2001]

You ask about the difference between thermal energy and mechanical energy. Both are two different forms of kinetic energy, which is the energy of motion. All types of kinetic energy can be categorized as radiant energy, thermal energy, sound energy, electrical energy, and mechanical energy; therefore, thermal energy does not cover all forms of kinetic energy.
Mechanical energy is sometimes called “motion energy,” and this is the main reason for misunderstanding because, in this case, “motion energy,” as the other name for mechanical energy, does not capture every type of energy of motion.

I should of been more specific in my definition of heat.
I know that heat is the transfer of energy from one system to another (d/t differences in temperature).
I would appreciate more of an insight into organised vs disorganised motion when it comes to the question,
however,
I do think my answer was on the right track.

 

[sol_2001]

Is that the exact wording of the question? I ask because in scientific usage "heat" only refers to the transfer of energy between bodies. Molecular motion within a body is "internal thermal energy". See e.g. https://en.wikipedia.org/wiki/Thermal_energy.
If that is the wording, your answer looks good enough.

It is interesting to consider intermediate scenarios. What about a system consisting of two balls orbiting each other? Two million balls? https://en.wikipedia.org/wiki/Maxwell's_demon

I should have been more clearer.
I know that heat is the transfer of energy from one system to another, dependant on the temperature difference, the system with a higher temperature will transfer heat to the system with a lower temperature.

 

[Herman Trivilino]

I would appreciate more of an insight into organised vs disorganised motion when it comes to the question,

You would have to give us Feynman's exact wording of the question.

 

[DaveC426913]

*Ahem*

I should of been more specific..

should have been

Careful with your diction in homework assignments.

 

[sol_2001]

*Ahem*

should have been

Careful with your diction in homework assignments.

Not a homework assignment, I'm too old for that.

 

[Lnewqban]

I would appreciate more of an insight into organized vs disorganised motion when it comes to the question,

How would you define organized and disorganized types of motion?
To me, your answer is correct.

Thermal energy is all about the frequency rate at which a group of molecules vibrate or oscillate.
Transfer of that thermal energy is all about the rate at which molecules interact or collide with other molecules located near by (think of a domino effect).

If our rapidly moving cool baseball is interacting with surrounding air, we may see transfer of thermal energy between the molecules forming the ball and the air molecules (think of the fast re-entry of space artifacts into the atmosphere).

 

[Vincf]

I don't know if that answers the question. One possible answer would be that you can convert all the kinetic energy of the "cold" ball into work, whereas you are limited in this conversion by the second law of thermodynamics if you want to use the internal energy of the "hot" ball.

 

[weirdoguy]

All types of kinetic energy can be categorized as radiant energy, thermal energy, sound energy, electrical energy, and mechanical energy;

Where did you get that from? Mechanical energy is something more than kinetic energy - it includes potential energy. Electric energy is also something different.