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As shown in , there are three different classes of levers defined by the relativepositions of the fulcrum, effort, and load. A first class lever has the fulcrum positioned between the effort and the load. Examples of first class levers include: abalance, a crow bar, and scissors. In a second class lever the load is placed between the fulcrum and the effort. Examples of second class levers include: awheelbarrow, a bottle opener, and a nutcracker. Third class levers place the effort between the fulcrum and the load. Examples of a third class lever are a hammer, afishing rod, and tweezers. Most machines that employ levers use a combination of several levers, often of differentclasses.

The wheel and axle

Both levers and the inclined plane lower the force required for a task at the price of having to apply that force over a longer distance. With wheels andaxles the same is true: a poweful force and movement of the axle is converted to a greater movement, but less force, at the circumference of the wheel. In a circular geometry, torque is a more useful concept than force and distance. You can learn more about torque here . The wheel and axle can be thought of as simply a circular lever, as shown in . Many common items rely on the wheel and axle such as the screwdriver, thesteering wheel, the wrench, and the faucet.

The Wheel and Axle

Gears and belts

A wheel and axle assembly becomes especially useful when combined with gears and belts. Gears can be used to change the direction or speed of movement, but changing the speed ofrotation inversely affects the force transmitted. A small gear meshed with a larger gear will turn faster, but withless force. There are four basic types of gears: spur gears, rack and pinion gears, bevel gears, and worm gears. Spur gears are probably the type of gear thatmost people picture when they hear the word. The two wheels are in the same plane (the axles are parallel). With rack and pinion gears there is one wheel and one rack, a flat toothed bar that converts the rotary motioninto linear motion. Bevel gears are also known as pinion and crown or pinion and ring gears. In bevelgears, two wheels intermesh at an angle changing the direction of rotation (the axles are not parallel); thespeed and force may also be modified, if desired. Worm gears involve one wheel gear (a pinion) and one shaft with a screw thread wrapped around it. Wormgears change the direction of motion as well as the speed and force. Belts work in the same manner as spur gears except that they do not change the direction ofmotion.

In both gears and belts, the speed and force is altered by the size of the two interactingwheels. In any pair, the bigger wheel always rotates more slowly, but with more force. On both the big and the small gear, the linearvelocity at the point of contact for the wheels is equal. If it was unequal and one gear were spinning faster than theother at the point of contact then it would rip the teeth right off of the other gear. As the circumference of thelarger gear is greater, a point on the outside of the larger gear must cover a greater distance than a point on thesmaller gear to complete a revolution. Therefore the smaller gear must complete more revolutions than the larger gear inthe same time span. (It's rotating more quickly.)

Questions & Answers

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Notes on basic mechanics for rice elec 201. OpenStax CNX. Jun 12, 2006 Download for free at http://cnx.org/content/col10357/1.1
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