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. 13 Bottle Opener 14 Work = Force x Distance 15 Bit (horse) 16 Velocity Ratio

[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) blah blah blah and so on

Agreed. Confusion arose because some people define 'effort' = work = energy. Replaced 'effort' with 'force'. Still not very well worded, but at least it's less ambiguous !--195.137.93.171 10:23, 15 September 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)

So the '1st vs. 2nd' terminology is ambiguous and unhelpful ! --195.137.93.171 10:25, 15 September 2007 (UTC)

If the paddle is left in as an example, I think the above should be made clearer - from the point of view of a paddler, it seems more intuitive that one of the two hands on the paddle is the fulcrum, so it appears that putting the paddle under 2nd class levers is an error. And is a springboard really a lever? It seems to me that the effort is the person bouncing on the end, and the load would therfore be the force pushing them back up - this does not obviously fit into the description of a lever. NorthernSpinney 29.2.08 —Preceding unsigned comment added by NorthernSpinney (talk • contribs) 12:26, 29 February 2008 (UTC)

The prose describing the 3rd class lever appears to work hard to justify it's usefulness. Most backhoes, cranes and bulldozers use hydraulic lifts within a third class lever. Thy hydraulic cylinder can give plenty of force so multiplying force is not necessary, while getting more distance is what the lever is useful for. I think it should be made clear in the description of the second class lever that it always multiplies force and in the description of third class lever that it always multiplies distance. The first class is first class because it can do both.

 —Preceding unsigned comment added by Shutoffyourtv (talk • contribs) 07:50, 6 January 2008 (UTC) 

More examples: Ice tongs = third class (paired) Paper cutter, guillotine style = second class I think you should get rid of the wrench example - too sketchy. 71.131.192.217 (talk) 09:04, 7 January 2008 (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 fuThis 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 lcrum, 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)

For most drawings of third class levers, you need to assume that the fulcrum is actually attached to the plank, while still allowing free rotation. Like a door hinge. Applejuicefool (talk) 17:01, 26 November 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)

Costing a lever of that length might make it a little impractical, not to mention giving him the pivot ... Time doesn't come into it : even if power is limited, he didn't say how far or how fast he would move it !

--195.137.93.171 10:41, 15 September 2007 (UTC)

I think the Archimedes quote should appear on the main page(with a bit of research, of course): It is thought provoking on such a traditionally dull subject. Shutoffyourtv (talk) 07:57, 6 January 2008 (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)

[edit] Bottle Opener

Isn't a bottle opener 2nd class and not 1st? The fulcrum is on the end and the load is in the middle.

I think there exist both types. The 2nd class is slightly better ergonomically, but those that are made as 1st class types both use less material, are shorter and thus easier to carry in ones pocket, foldable into a swiss knife or attached to a keyring. My understanding is that the former are generally used in fixed locations such as bars where the ergonomy matters more, but for occasional use as a carryable or swiss knife implement they are usually the latter. I might of course be wrong. -- Cimon Avaro; on a pogostick. 13:59, 9 July 2007 (UTC)

[edit] Work = Force x Distance

Under "Theory of Operation", while it is true that Work = force x distance, this distance is not the same as the lever arm (the distance from the fulcrum to the effort or load). I think the relevant principal is the balancing of torques, where the torque is the cross product of force and lever arm, which becomes torque = force x lever arm if the force is perpendicular to the lever.

Adam 71.41.190.154 (talk) 20:18, 14 February 2008 (UTC)

[edit] Bit (horse)

Some kinds of bit (horse) involve levers; some provide mechanical advantage (ie, not = 1), others don't. Could someone here "sanity check" the article, and related articles on particular kinds of bit, to ensure these bits are not described as violating any law of physics? --Una Smith (talk) 21:36, 28 February 2008 (UTC)

[edit] Velocity Ratio

Velocity ratio should be mentioned in this article (or it should have an article of its own and be referenced from here). SpinningSpark 13:02, 30 March 2008 (UTC)