Effort vs Work

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So, I want to understand the difference between effort and work applied to this situation:

A) Lift/push 1kg a distance of one meter, repeat with 2kgs. How much more effort does it take to lift/push 2kgs instead of 1kg?

B) Lift/push 1kg a distance of one meter, repeat with a distance of two meters. How much more effort does it take to lift/push 1kg two meters instead of one?

C) If work is defined as "effort," how would you say work depends on the force applied and on the distance moved.

Currently, I say A) about the same, B) double, C) dependent on distance.
Verdict? Right, wrong?

Thank you!
 

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  • #2
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*Update: okay, so I went and performed this experiment with a couple of biology books. It turns out that double the mass, same distance, took a lot more effort than the same mass double the distance. So, I'm thinking that if work is defined as effort, it would be dependent on force more than displacement. However, this isn't quite what the book says. So, now I'm a bit confused as to how effort and work correlate to each other.
 
  • #3
Doc Al
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So, I'm thinking that if work is defined as effort, it would be dependent on force more than displacement. However, this isn't quite what the book says. So, now I'm a bit confused as to how effort and work correlate to each other.
Whoever wrote that book should be shot! :smile: "Effort" is a loosely defined biological/physiological concept that is not directly equivalent to work. For example, if I tell you to hold a heavy weight in your hands for a certain amount of time without moving, I think you'll say that it takes 'effort' but since you're not moving no work is done on the mass. (Work will be done internally, within your muscles, but that's something else.)

What book are you using? What does it say about 'effort' versus 'work'?
 
  • #4
Dale
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Work is force times distance. I have no idea what effort is.
 
  • #5
russ_watters
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If I had to invent a definition, I'd say "effort", as it is commonly used in layman's terms, is the number of calories you burn to accomplish a certain task (over and above your resting burn rate).

Obviously, in many situations, there is no corellation at all between "effort" and "work".
 
  • #6
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Wow that gave me a good laugh
 
  • #7
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Haha, Doc Al! I've been in the mind-set a few times before, too. :) Actually, the book is a great one: Physics for Scientists and Engineers: A Strategic Approach (Knight). The experiment I was doing was out of a parallel lab unit, and the purpose was the demonstrate to us how an everyday definition of "work," like lifting weights, is not actually work by a physicist's definition. It took blowing the experiment up from 1kg masses to big annoying bio books, but I actually got the difference--when all else fails, go bigger. :)

Thank you for your help, all of you!
 
  • #8
Doc Al
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Actually, the book is a great one: Physics for Scientists and Engineers: A Strategic Approach (Knight).
That is a good book.
The experiment I was doing was out of a parallel lab unit, and the purpose was the demonstrate to us how an everyday definition of "work," like lifting weights, is not actually work by a physicist's definition.
I'm happy to hear that. :wink:
 

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