LEVERS

They help us to move ourselves… or other objects.

Levers are used to apply forces.

The Scientific Part!

Parts of a lever

Within the lever are three components that we need to understand -

•Fulcrum or Pivot - the point about which the lever rotates

•Load or Resistance - the force applied by the lever system. Load to be moved (which includes lever itself)

•Effort or Force - the force applied by the user of the lever system – the force which causes movement

There are three classes of levers

The class of lever is dictated by the arrangement of the 3 components:

1st Class LeverThe fulcrum lies between the effort and the load

e.g see-saw, crowbars

2nd Class Levers The load lies

between the effort and the fulcrum

Eg wheelbarrow

3rd Class Lever The effort lies

between the load and the fulcrum

Eg tweezers & most muscles.

Force Arm & Resistance Arm• The distance from the fulcrum (pivot) to the point of

force (effort) is called the FORCE ARM

• The distance from the fulcrum (pivot) to the point of resistance is called the RESISTANCE ARM

Lever characteristics

Long resistance arm: speed and range of movement

Short resistance arm: force

FUNCTIONS OF LEVERSAll levers have 2 functions:

• They either:

1. Increase the speed at which an object can move with a given effort.E.g. driver as opposed to an iron in golf

2. Increase the resistance that can be moved with a given effortE.g. Wheelbarrow – can lift a big weight that would not be able to lift alone

Mechanical advantage

• If Resistance arm is longer, lever is better for force

• If Resistance arm is shorter, lever is better for speed

• In 2nd class levers resistance arm is always longer, therefore 2nd class levers are better for strength or force

• In 3rd class levers force arm is always longer, therefore 3rd class levers are better for speed

The Application Part!

So… what happens when a golfer uses different clubs?

• The longer the lever the greater the speed.

• What about control?

• Which is easier to control and hit straight – an iron or a driver?

Question

• In badminton, why is it easier to teach children to hit the shuttle with a shorter racquet?

Debate

“Short people are stronger than taller people”