Archimedes' wheel

  • Thread starter ryukyu
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  • #1
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I am going to be doing a demonstration of Archimedes' wheel for some 6-9 year-old students and would like to try to figure out the work done by the wheel to lift 10 liters of water 1m vs the lifting of a 10 liter pale the same height.

Anyone know of a way to easily figure the work done in turning the screw if I were to fill the screw completely and turn it?

I am an electrical engineering guy so this is outside my comfort zone, but would appreciate anyone who is willing to work through it with me.
 

Answers and Replies

  • #2
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Neglecting friction forces the work is the same because every turn raises the same amount of water the same distance.
What Archimede's screw acomplishes is a reduction of applied force.
If you have a long handle, every time you turn it 360 degrees, your hand travels a long distance. Thus, the required force is smaller.
The same happened with old-fashioned car jacks. A long handle turned a fine-pitched screw
 
  • #3
tiny-tim
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Another big advantage is that it can't spill any water, unlike most other methods. :biggrin:

Are you seriously going to teach 6-9 year olds about work and energy?

Or is this an excuse for a field holiday working in your diamond mine? o:)

(btw, it's Archimedes' screw … a google image search for Archimedes' wheel shows an ordinary worm gear for lifting a bucket out of a well :wink:)
 
  • #4
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Thanks for the replies thus far.

@tiny-tim: No I am not aiming to teach them about work and energy, but I do like to back my demonstrations with math when I make claims like "this takes less work than this.." especially when parents start asking questions.

@Godianus: I'm not making the connection. It seems like it would take less work (since there is less applied force). I guess I should make the experiment to state 1m up and 1m right, indicating the use of an inclined plane as well.

So, neglecting friction, this is not less work than lifting a bucket 1m and moving it right 1m?
 
  • #5
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The word propeller conjures images of helicopters, beanie hats, and toy boats. However, in the early 1800s propellers generally meant paddle-wheels. That began to change with the launch of the Archimedes in May of 1839. The ship was unique in an age of paddle-wheel steamers. The Archimedes was steam powered, but was not propelled by paddle-wheels. Instead, she was fitted with a device described to the patent office as "an improved propeller" in the shape of "a sort of screw, or worm." The Archimedes was only the first in a series of practical screw-propelled ships.
 
  • #6
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Thanks for the replies thus far.

@tiny-tim: No I am not aiming to teach them about work and energy, but I do like to back my demonstrations with math when I make claims like "this takes less work than this.." especially when parents start asking questions.

@Godianus: I'm not making the connection. It seems like it would take less work (since there is less applied force). I guess I should make the experiment to state 1m up and 1m right, indicating the use of an inclined plane as well.

So, neglecting friction, this is not less work than lifting a bucket 1m and moving it right 1m?

Yes, Archimedes' screw doesn't reduce the amount of work, we apply less force but our hand travels a longer distance.
 
  • #7
cjl
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Thanks for the replies thus far.

@tiny-tim: No I am not aiming to teach them about work and energy, but I do like to back my demonstrations with math when I make claims like "this takes less work than this.." especially when parents start asking questions.

@Godianus: I'm not making the connection. It seems like it would take less work (since there is less applied force). I guess I should make the experiment to state 1m up and 1m right, indicating the use of an inclined plane as well.

So, neglecting friction, this is not less work than lifting a bucket 1m and moving it right 1m?

Correct. It requires less force, but that force is applied over a significantly larger distance. Neglecting friction (and the mass of the bucket), the work should be the same.
 

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