Talk:Lever

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Contents 1 incorrect math 2 Classes 3 Archimedes screw 4 Levers 5 The Fulcrum 6 More examples 7 Archimedes' quote 8 add an example 9 Examples 10 Scissors 11 Third-class levers 12 Italics are cramming the adjacent text.

[edit] incorrect math

In the intro it says that the lever allows less force to move soemthing a greater distance. This is not true. Work=force times distance, so if both force and distance are lowered in the effort, then work must also change. this is impossible, there is no such thing as a work eliminating machine. all a simple machine does is exchange force for distance or vice versa Beefpelican 02:52, 8 February 2007 (UTC)

[edit] Classes

I'm unsure, but it appears to me that the description of the 1st and 2nd class levers are switched around. The book im looking at (American School Physical Science Study Guide) has these levers listed as the opposite. Basically, the 1st class lever on wikipedia is listed as 2nd class in book, and 2nd class on wikipedia is listed as first class in the book. If anyone can clear this up that'd be great. Thanks!

My twelve-year-old daughter says that they are not mixed up in this article.

Is there a class like class 1 where the effort is closer to the fulcrum than the load or is that still concidered class 1? Tsinoyboi 11:15, 22 September 2006 (UTC)

• That's still class oneBeefpelican 02:47, 8 February 2007 (UTC)

Of course 1st and 2nd class levers can be switched around. It all depends on the use: for if you're using a canoe paddle as a 2nd class lever; the water is the fulcrum, the bottom hand is the output/canoe, and the top hand is the input. The output/bottom hand (canoe) travels in the same direction as the input/top hand. However; once the water begins to travel backwards, it ceases to be a fulcrum, and the bottom hand becomes the fulcrum. The top hand remains the input, for the lever is now used as a 1st class lever to move water (output) in the opposite direction. My favorite 2nd class lever is the oar of the row boat, which is usually incorrectly illustrated as a first class lever: showing the oarlock as the fulcrum, and the water as the resistance. Since the rowboat actually moves in the direction of the force, the oarlock is actually the load, and the water is the fulcrum (with the oar's blade remaining fixed in location). Kinipopo 10:11, 24 March 2007 (UTC)Kinipopo 09:54, 15 February 2007 (UTC)

[edit] Archimedes screw

This sentence: Archimedes also invented Archimedes' screw, which was used to draw water from a lake or river, although this falls under the screw category. has nothing to do with levers - should it be removed? —The preceding unsigned comment was added by 203.59.154.246 (talk • contribs) .

Quite right. I have done so. Anyone interested in other work by Archimedes can check his article. -- Ec5618 18:04, 1 February 2006 (UTC)

[edit] Levers

The levers here are correctly labelled. I was wondering if you could tell me what machines (levers) have a mechanical advantage of one.

• The ideal mechanical advantage of a lever is defined as the length between the effort and fulcurm divided by the length between the resistance and the fulcrum, or d_e/d_r. thus, if the effort and resistance are equdistant, then the mechanical advantage equals one. an example of this is a first class lever with the fulcrum in the middle and a weight (the reistance and someone's hand (the effort) at either end. also an old fassioned scale. Beefpelican 02:43, 8 February 2007 (UTC)

The 3rd class lever is incorrectly drawn, for the fulcrum is in the wrong position and renders the lever useless. Since input and output travel in the same direction, the fulcrum should be inverted directly above its existing position in order for the lever to work properly. Try using a broom with the fulcrum positioned as drawn - it just won't work. Now position the fulcrum opposite as drawn - it now sweeps. Kinipopo 09:36, 24 March 2007 (UTC) Kinipopo 09:14, 15 February 2007 (UTC)

[edit] The Fulcrum

Does the "plank" need to sit ontop of the fulcrum to be a lever? Or can the fulcrum/pivot go through the plank and still be a lever? I'm curious to know if a two-prong propeller counts as a lever. 205.174.22.28 01:46, 23 July 2006 (UTC)

The fulcrum is the pivot point, so it can go through such as in scissors. I don't know what you mean by two-prong propellers. propellers in general act more like wheels (though, wheels and gears work on the same principle as levers), but the pushing air part might be more of either Screw (simple machine) or Airfoil or both. Tsinoyboi 11:00, 22 September 2006 (UTC)

[edit] More examples

Maybe it should be included how Engineering vehicles use levers along with hydraulics and other simple machines. Perhaps even just saying that in general could be enough. Cranes, for example, use one or more class of lever. I aded engineering vehicles in see also. should that be moved or removed? Tsinoyboi 11:22, 22 September 2006 (UTC)

[edit] Archimedes' quote

Archimede is supposed to have said:

Give me the place to stand, and I shall move the earth.

While this may be theoretically true, has anyone actually performed the maths to figure out the practicality with respect to time spent exercising a certain amount of energy, etc.? Just curious. :-) --Frodet 13:47, 27 September 2006 (UTC)

Yes, I'm sure somebody has performed the math -- it's not like it's difficult. dougmc 23:28, 22 March 2007 (UTC)

[edit] add an example

add a simple example of calculating lavarage formulat near to the image is bad the formula should be bigger. and a proof of the direvation from newton law

[edit] Examples

i'm not sure if some of the second and third class levers listed are actualy third class, for example the crowbar. this is a first class lever, and is listed as such earlier. if nobody says anything in about a week (casue i'm not an expert) i'll remove the bad examples.

[edit] Scissors

Aren't scissors and pliers in the third class?

Arithmetics 05:02, 26 March 2007 (UTC)

[edit] Third-class levers

Under the picture of the topic "Third-class levers", the last sentence says "White Mercury is a band, check us out on www.youtube.com".

What the heck, advertisement.. Too bad some people just won't show respect to the people contributing to this site. Thank you.

[edit] Italics are cramming the adjacent text.

It never fails when italics are used it causes a crammed letter issue if used for any emphasis, such as in the word fulcrum for example. I suggest bold, underscore or both be used. --RonEJ 12:29, 28 March 2007 (UTC)