Re: [DMCForum] Re: You're both wrong! Attn: Rick/Martin

[Farrar Hudkins <fhudkins@xxxxxxx>]

Rich:

Yep!

> In order to hold the torque wrench to 20 ft/lbs. that requires the 
> expenditure of energy. Is not the expenditure of energy by 
> definition, work?

True, work is being done, but as I understand it, the work is being done 
to counteract the force of gravity.

> Well, maybe not. Supposed you tied the handle to something to hold 
> the wrench. Then no one & nothing is expending energy. There -is- 
> however, "potential" energy in the tension of the wrench handle. If 
> the rope snapped, and the wrench flew off that would be latent? 
> energy (energy in use/motion) and work would be done because the 
> wrench moved.

IIRC, potential energy lies in the wrench because it isn't falling to 
the ground. Gravity creates this potential energy. Kinetic energy is 
when it moves, which is when you let go of the wrench. You're expending 
energy to prevent the wrench from falling, but the energy you're 
expending is exactly the amount of energy necessary to counteract 
gravity. So you ARE doing work by preventing the thing from being moved 
by gravity, if you're holding it yourself.

Now we have to think about Newton's first law of motion, which states 
that an object in motion tends to stay in motion unless prevented from 
doing so by a force. This is comparable to Galileo's law of inertia.

Inertia is what I'd like to think of when examining the rope thing. And 
let's not forget that friction is a force, and so is gravity.

If an object tends to stand still unless moved by a force, or remain in 
motion unless stopped by a force, then let's think about your house. 
Your house has great inertia. It's being held to the ground by, for our 
purposes, gravity and inertia. If you tie a rope to the ceiling to keep 
a wrench from falling to the ground, you're setting the SMALL pull of 
gravity on a wrench against a LARGE amount of inertia on your house.

Wait. There's probably a better way to explain this. Sorry.

Farrar

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