Archimedes (Greek mathematician, 287 to 212 B.C.) said, “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.”
Levers are the simplest of machines, simpler even than the wheel. Unlike the wheel levers occur naturally in animal and plant life. Lifting your arm uses several levers as does nodding your head. The lever is simply different.
There are three types of lever.
Type 1 lever
This type of lever has a load at one end and a force at the other with a fulcrum in the middle.
Type 2 lever
This type of lever has a load in the middle and a force at the one end with a fulcrum at the other.
Type 3 lever
This type of lever has a load at one end and a force in the middle with a fulcrum at the other end.
What type of lever do these items use? Do any of them use more than one lever to operate?
see-saw, tweezers, wheelbarrow, stapler, fishing rod, bottle opener, hammer’s claws, pliers, nut cracker, tongs, scissors, nail clippers.
Can you add anything to this list?
Now think about your own body.
What sort of lever is required to move your head in a nodding motion? Imagine your spine as the fulcrum, the muscles in your neck as the force and your skull as the load.
Hold your arm out in front of you and flex your bicep so that your upper arm is stationary and only your forearm moves. What are the fulcrum, force and load and what sort of lever can you see? Is the same sort of lever involved when you move your arm back to being straight in front of you? Is there a different force being exerted\muscle being used?
Do all movements in the human body rely on some sort of lever or can you think of any moving parts of the body that don’t involve levers?
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.
- Record the weight of the adult and the child and measure the distance from the people to the fulcrum. Can you work out the ratio for child weight and distance to adult weight and distance?
You will need:
- An ruler
- A tape measure
- Some light food like cereal
- A pencil
- Some small cups
What to do:
Put the ruler 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?
Record your findings in a table. Distance from fulcrum and distance fired.
Could the other types of lever be used like this?
Can you find of any inventions that operate like this?
Don’t forget to tidy up your mess.
Can you think of any other experiments?