lever logic... levers made simple
So what’s the big deal about levers? Well, they are simple machines that help make your life easier. Have a look at this...
There was a dull Crack! as the crowbar prised its way through the locked door. The door swung open. Freddie ‘Fingers’ Force had done it again. Quickly he took out a pair of scissors and snipped out the photo from the document lying on the table.
Using the tweezers from his pocket he picked it up and laid it over a clean sheet of paper. He looked around for the stapler and attached it.
“Nice work, Force” grinned Detective Inspector Fulcrum leaning on the door handle. Force pivoted. “And you even brought a wheelbarrow with you to load the swag”. He chuckled. “All that effort…”“Wait just one moment Fulcrum. Look at this.” growled Force, stretching out his arm and extending the photo. Fulcrum turned. “It’s Lenny ‘The Spring’ Load! I thought he was in for a long stretch?”
“No. He was sprung last week – inside job – he was catapulted over the prison wall using a seesaw”. Force nonchalantly opened a beer with his bottle opener. “Of course I know where he’s hanging out… that pub on the other side of the river - The Claw Hammer and Tongs”
Fulcrum pondered “So between us we could nail him. This time Load’s going down for good. I can see the headlines now…
“Force and Fulcrum make easy work of Load”‘’
did you spot all the levers? what is it all about?
Well a lever consists of three parts; a fulcrum (the point about which the lever pivots or turns), the load (the part you are trying to move) and the effort or force you are using to move it.Levers allow you to move a large load with a small effort. The further the effort is from the fulcrum, the easier a lever is to move so in general long levers are more useful.
In most cases levers help you to turn a small force into a much larger one. Take for example opening a tin of treacle – can you do it with your fingers? No! You use a knife as a lever. By exerting a small force at one end of the lever you create a much larger force at the other end which prises the lid off.
Have you ever tried opening a door by pushing it near the hinges? Not half as easy as pushing it with the door handle is it?
Thank goodness for levers!
There are three classes of levers.
class 1 lever 
This is where the fulcrum is between the effort and the load. An example of a Class 1 lever is a see saw.
If you push down on one end (effort) it will raise the load on the other end.
class 2 lever
In this case the load is between the fulcrum and the effort. An example of a Class 2 lever is a wheelbarrow. You pull up on the handles (effort) to raise the load in the middle and the wheel (fulcrum) is at the end.
class 3 lever
In this case the effort is between the fulcrum and the load. An example of this is a fishing rod.
One hand acts as the pivot (fulcrum), the other hand is placed in the middle of the rod and pulls (effort) and the fish (load) is hanging off the end! It was THAT big!
For more information and animations on levers see this site and to get a better idea of lever applications
lifting activity
Archimedes (Greek mathematician, 287 to 212 B.C.) said, “Give me a place to stand and I will move the Earth,” meaning that if he had a lever long enough, he could move the Earth by his own effort. At the very least we can show that a child can lift an adult:
You will need:
An adult
A child
A brick or block of wood
A plank of wood 1 inch thick and at least 4 feet long
What to do:
Make a lever by placing the plank over the wood block.
To take advantage of the properties of the lever, make sure the fulcrum (wood block) is closer to the end of the lever on which the adult will stand.
Have the adult stand on the short end and the child stand on the long end.
What happens?
If the child cannot lift the adult, adjust the fulcrum so that it is closer to the side on which the adult is standing.
What is happening?
The plank of wood acts as the lever.
A smaller load (child) at a greater distance from the fulcrum will cause a greater force downwards than a large load (adult) at a short distance from the fulcrum.
So the ‘seesaw’ is unbalanced and the adult goes up.
It is all about balanced and unbalanced forces.
catapult shooter
You will need:icelolly stick
metre stick or tape
CheeriOs or other cereal
pencil
small cups
What to do:Put the icelolly stick across the pencil.
Put a piece of cereal on the end of the stick touching the table.
Flip the cereal by hitting the stick end that is in the air.
Mark where the pencil (fulcrum) is.
Record the distance that the cereal travelled.
Now place a small cup at this distance.
Fire again and see if your cereal lands in the cup.
Try moving the fulcrum. What happens now?
What is happening?
The icelolly stick is acting as a Class 1 lever. The pencil (fulcrum) is in the middle and the cereal (load) is at one end. By hitting the other end of the stick we are providing the effort that will lift the load into the air.
By placing the cereal as far away from the fulcrum as possible we will be able to move it with the greatest force and so it should travel a greater distance.
Think back to medieval times and the huge boulder-slinging catapult-like machines known as trebuchets. The trebuchet was introduced into Europe in the 12th century. In early and smaller trebuchet, the downward force came from many people pulling "down the shorter end of the beam which flipped up the longer end."
Take a look at this site if you want to know more about the amazing history of the Trebuchet.
What have the Romans ever done for us, eh?
things to do
Who’s that trip-trapping …? Try making a Pop-up Troll.Tie Me Kangaroo Down Sport.
‘Strewth mate! Get that Joey under control.
How good are you at balancing things? Try this surreal game based on levers. Watch out for the octopus!
Have a look at all the different kinds of simple machines you can see around the home. Can you spot any levers?
lesson ideas for teachers
Using levers to balance loads
Effect of moving the fulcrum
Playground Physics - Seesaw physics
Building a lever balance
Detailed information about levers and activity ideas (word document)
Simple Machines Teacher’s GuideAnimation of the movement of leversApplying knowledge of levers