Testing the TK Tar Baby

[mrsean2k]

Work done is  force x distance moved -  work done is independent of the time it takes to do it (although your human experience might tell you that prevaricating over an unpleasant job takes longer and requires more effort overall, and in fact one's personal intuitive experience of what "work" involves is misleading).


When you raise a brick a meter in the earths gravitational field, does the potential energy you endow it with depend on how long you take to get it there?


Will it hurt your foot more or less when it drops, dependent on whether it was catapulted into place or raised using a tortoise and a system of pulleys?

[TinselKoala]

Work done is  force x distance moved -  work done is independent of the time it takes to do it (although your human experience might tell you that prevaricating over an unpleasant job takes longer and requires more effort overall, and in fact one's personal intuitive experience of what "work" involves is misleading).


When you raise a brick a meter in the earths gravitational field, does the potential energy you endow it with depend on how long you take to get it there?


Will it hurt your foot more or less when it drops, dependent on whether it was catapulted into place or raised using a tortoise and a system of pulleys?

Thank you.

And while ALL units ultimately come down to length, charge, mass and time in various combinations, there is a real difference between having a "seconds squared" term in a denominator .... and a RATE of something PER second.

The ability to do work... energy ... is different from the rate at which the work is performed... power. A Joule is a Joule even when it's sitting in a capacitor doing crossword puzzles or whatever they do in there and will be the same forever unless it leaks out. A watt isn't anything at all unless some Joules are acting PER a time period. When your car is sitting still, how many miles will you go in an hour?

[Groundloop]

Work done is  force x distance moved -  work done is independent of the time it takes to do it (although your human experience might tell you that prevaricating over an unpleasant job takes longer and requires more effort overall, and in fact one's personal intuitive experience of what "work" involves is misleading).


When you raise a brick a meter in the earths gravitational field, does the potential energy you endow it with depend on how long you take to get it there?


Will it hurt your foot more or less when it drops, dependent on whether it was catapulted into place or raised using a tortoise and a system of pulleys?

mrsean2k,

The definition of a Joule =  ((kg*(m*m)/(s*s). See the s in there? It is the seconds you used to move the mass.

GL.

[mrsean2k]

GL, as TK alludes in his post, that s² term isn't anything to do with the amount of time it takes to move the mass. It's a counter-intuitive artefact of the way these units are ultimately derived.



When I wind my watch, the amount of energy stored in the spring - the work done - is identical no matter whether I wind it at the rate of 1/4 turn per week, or in one frenzied burst.


I put a brick on one end of a see-saw, and a pail on the other. I run a hose into the pail. It doesn't matter whether I turn the tap on full, or it barely drips, by the time the brick has been raised, the same work has been done; the brick has the same additional potential energy - also measured in Joules - in each case.

[Groundloop]

Thank you.

And while ALL units ultimately come down to length, charge, mass and time in various combinations, there is a real difference between having a "seconds squared" term in a denominator .... and a RATE of something PER second.

The ability to do work... energy ... is different from the rate at which the work is performed... power. A Joule is a Joule even when it's sitting in a capacitor doing crossword puzzles or whatever they do in there and will be the same forever unless it leaks out. A watt isn't anything at all unless some Joules are acting PER a time period. When your car is sitting still, how many miles will you go in an hour?

TK,

A Watt = Voltage * Ampere and is a timeless unit. A Watt is used to describe what is happening right now in a circuit.
A Watt per Second is not timeless and describes the work done during that time in that circuit.
A Joule is 1 Ampere during 1 Second into 1 Ohm and is a description of work done during that time.
A joule is not a timeless unit. Never has been, never will be. 1 Joule = ((1kg*(1m*1m)/(1s*1s) or 1A*1s into 1 Ohm.
So if you say 1 Joule per Second then this is the same as ((1kg*(1m*1m)/(1s*1s)*s or (1A*1s into 1 Ohm)*1s.
And that is a description of the RATE of CHANGE of the work done and not a Joule. Do you see the difference?
A Joule is NOT a Watt. A Watt is NOT a Joule. A Joule is a Watt per Second. So a Watt per Second is also a Joule.
A Watt per Second per Second is a rate of change in a circuit and is NOT a Joule, but a Joule per Second.

GL.