LEVERS. They help us to move ourselves…or other objects. Levers are used to apply forces

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”