Levers n Levers are one of the simple machines that were probably used in prehistoric times. Levers were first described about 260 BC by the ancient Greek

LeversLevers

Levers are one of the simple Levers are one of the simple machines that were probably used machines that were probably used in prehistoric times. Levers were in prehistoric times. Levers were first described about 260 BC by the first described about 260 BC by the ancient Greek mathematician ancient Greek mathematician Archimedes (287-212 BC).Archimedes (287-212 BC).

LeversLevers

A leverA lever is a simple machine that is a simple machine that makes work easier for use; it makes work easier for use; it involves involves moving a load around a pivot using a moving a load around a pivot using a force.force. Many of our basic tools use Many of our basic tools use levers, including scissors (2 class 1 levers, including scissors (2 class 1 levers), pliers (2 class 1 levers), levers), pliers (2 class 1 levers), hammer claws (a single class 2 lever), hammer claws (a single class 2 lever), nut crackers (2 class 2 levers), and nut crackers (2 class 2 levers), and tongs (2 class 3 levers).tongs (2 class 3 levers).

LeversLevers

In physics, In physics, a levera lever is a rigid object is a rigid object that that is usedis used with anwith an appropriate appropriate fulcrumfulcrum or pivot point or pivot point to multiply to multiply the mechanical forcethe mechanical force that can be that can be applied to another object.applied to another object.

LeversLevers

The The lever allows less effort to be lever allows less effort to be expended to move an object a expended to move an object a greater distance.greater distance.

The three classes of leversThe three classes of levers

A first-class lever A first-class lever is a lever in which is a lever in which the fulcrum is the fulcrum is located in located in between the input between the input force and the force and the output force.output force.

Class 1 leversClass 1 levers

Examples: #Seesaw (also known Examples: #Seesaw (also known as a teeter-totter)as a teeter-totter)

1. Crowbar or claw hammer 1. Crowbar or claw hammer (removing nails)(removing nails)

2. Pliers (double lever)2. Pliers (double lever)


In a second-class In a second-class lever the input is lever the input is located to the far located to the far side of the bar, the side of the bar, the output is located in output is located in the middle of the the middle of the bar, and the fulcrum bar, and the fulcrum is located on the is located on the side of the bar side of the bar opposite to the opposite to the input.input.

Class 2 LeversClass 2 Levers

# Wheelbarrow# Wheelbarrow # Nutcracker# Nutcracker # Door# Door # Pry bar# Pry bar # Stapler# Stapler # Diving board# Diving board


Class 3 levers. The Class 3 levers. The input effort is input effort is higher than the higher than the output load. output load. However, also However, also notice that the notice that the input effort moves input effort moves through a shorter through a shorter distance than the distance than the output load.output load.

The Lever LabThe Lever Lab

To determine how levers change To determine how levers change the force required to move an the force required to move an object.object.

Way Cool LeversWay Cool Levers

The The trebuchet istrebuchet is a counterweight siege a counterweight siege engine. Basically, engine. Basically, aa lever and a slinglever and a sling. .

But First!………...But First!………...

A bit about Siege EnginesA bit about Siege Engines

Basically there are Basically there are three ways to three ways to power a machine that throws a power a machine that throws a projectile.projectile.– FlexionFlexion– Torsion Torsion – LeversLevers


FlexionFlexion– Which Which is theis the bending of a limb or leaf bending of a limb or leaf

spring.spring.– Bows, crossbows,Bows, crossbows, and the most ancient and the most ancient

of large Greek rock throwing and arrow of large Greek rock throwing and arrow throwing siege engines throwing siege engines were Flexion.were Flexion.

– The gastrophetes was the firstThe gastrophetes was the first recorded arrow throwing siege engine recorded arrow throwing siege engine showing up around 399 BC.showing up around 399 BC.




TorsionTorsion– They have arms similar to the limb of They have arms similar to the limb of

a bow on a crossbow, but a bow on a crossbow, but the arms the arms areare independently independently powered by powered by bundles ofbundles of semi-flexible sinew semi-flexible sinew cord cord wrapped into a frame of woodwrapped into a frame of wood which which are pretensioned are pretensioned and then twisted.and then twisted.

– Recorded Recorded first around 250 BC.first around 250 BC.



The two-armed ballista and The two-armed ballista and catapulta invented by the Greeks catapulta invented by the Greeks and later used by Romans was and later used by Romans was largely replaced by the Roman largely replaced by the Roman onager, which was a much simpler onager, which was a much simpler design, using only one arm to design, using only one arm to propel a rock with a sling.propel a rock with a sling.



In the early Middle Ages, walls and In the early Middle Ages, walls and fortifications had become taller fortifications had become taller and stronger than they ever were and stronger than they ever were in ancient Greek times, and the in ancient Greek times, and the stone castle was developed, which stone castle was developed, which had walls stronger than most had walls stronger than most ancient siege engines could ancient siege engines could destroy. destroy.


From the Mongolians in the east From the Mongolians in the east came the idea for a new type of came the idea for a new type of siege engine, powered by gravity siege engine, powered by gravity and designed for one purpose; to and designed for one purpose; to destroy walls. This was the destroy walls. This was the trebuchet.trebuchet.

TrebuchetTrebuchet

The The trebuchet is a Type-1 lever trebuchet is a Type-1 lever and a slingand a sling. In the Type-1 lever, . In the Type-1 lever, the force is applied to one end, the the force is applied to one end, the load is on the other end and the load is on the other end and the fulcrum sits between the two. fulcrum sits between the two.

TrebuchetTrebuchet

The The sling is the oldest projectile sling is the oldest projectile weaponweapon. There is a pouch to hold the . There is a pouch to hold the projectile and two long strings. Both projectile and two long strings. Both ends of the string are held in one ends of the string are held in one hand and the sling is swung around hand and the sling is swung around and around. Then, at the proper and around. Then, at the proper moment, one end of the sling is let moment, one end of the sling is let go with the other end is still held by go with the other end is still held by the handthe hand

TrebuchetTrebuchet

Historic Counterweight Historic Counterweight Trebuchet IllustrationsTrebuchet Illustrations

Trebuchet from The Romance of Alexander (circa 1330).


Trebuchet by Kolderer, c1507.


An early 14th Century trebuchet


A 13th Century "Mongol" trebuchet


A fixed-weight trebuchet from the early 16th Century

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Levers n Levers are one of the simple machines that were probably used in prehistoric times. Levers were first described about 260 BC by the ancient Greek