Levers

1st Class Levers2nd Class Levers3rd Class Levers

What is a Lever?

• A lever is a simple machine that is used to lift things.

• It is made up of a bar (called the lever stick) and a support (called the fulcrum).

Lever Stick

Fulcrum

Everyday Examples of Levers

• See-Saw• Nutcracker• Wheelbarrow• Broom• Can you think of any more?

Parts of a Lever

• There are different parts and sections of a lever.

• You have the fulcrum and lever stick.

• You also have a force side and a load side.

• The relationship between the position of the load side, fulcrum, and force side determines what class of lever it is.

Classes of Levers

• There are three different classes of levers.

• 1st Class: force side-fulcrum-load side• 2nd Class: force side-load side-fulcrum• 3rd class: load side-force side-fulcrum

1st Class Lever

• Structure of the 1st Class Lever: • Force Side-Fulcrum-Load Side

• The see-saw is an example of a first class lever.

• The force needed to lift the load decreases when the fulcrum gets closer to the load side.

2nd Class Lever

• Structure of a 2nd Class Lever• Force Side-Load Side-Fulcrum

• The wheelbarrow and the nutcracker are examples of a 2nd class lever.

• Again, The force needed to lift the load decreases when the fulcrum gets closer to the load side.

3rd Class Lever

• Structure of a third class lever• Load Side–Force Side–Fulcrum

• The broom is an example of a 3rd class lever.

• The load is the dirt or end of the broom, the force is your bottom arm, and the fulcrum is your top hand.

What type of lever am I (1,2,or3)?

1st Class

1st Class

2nd Class 2nd

Class

3rd Class

3rd Class

Wheels and Axles

Wheel and Axle

What is a Wheel & Axle?

• A wheel and axle is a simple machine consisting of a wheel that revolves (turns) around a post (axle).

• This simple machine makes it easier for us to move things from one place to another.

• The further the force is away from the axle, the easier it is to turn the wheel. This means that it is easier to turn a big wheel than a small wheel.

Pictures of Wheels and Axles

Common Examples

Pulleys

Fixed PulleyMovable PulleyBlock and Tackle

What is a Pulley?What is a Pulley?

• Pulleys are a kind of simple machine that consists of a rope that fits onto a wheel and changes the direction of a force.

• There are three kinds of pulleys.• Fixed Pulley• Movable Pulley• Block and Tackle (combo of fixed

and movable)

Fixed PulleyFixed Pulley

• Wheel attached to surface• Changes the direction of

the applied force• NO mechanical advantage

– same amount of force is required

Movable Pulley• Pulley moves along

the rope• Wheel supports the

load• Effort is in the same

direction as movement• Reduces the forces

needed to move an object

Block and Tackle

• Has at least two wheels (one movable and one fixed)

• The more complex the pulley, the more the effort needed to move the object decreases

Common Examples Of Pulleys