Levers

effort resistance A lever consists of a rod or bar that rests and turns on a support called a fulcrum.

A force of effort is applied at one end of the rod to lift a load placed at the other end. A lever can help lift a weight with less effort. effort resistance fulcrum

Prying something loose with a crowbar is using a lever Prying something loose with a crowbar is using a lever. Some machines, such as a catapult, use a lever to hurl objects.

Here is a catapult you could make.

Three Classes of Levers First Class Lever The fulcrum is between the effort force and the resistance force. effort resistance fulcrum

Three Classes of Levers Second Class Lever The resistance is between the effort and the fulcrum.

Three Classes of Levers Third Class of Lever The effort is between the fulcrum and the resistance.

First Class Lever Second Class Lever Third Class Lever

Levers in the Body How bones and muscles work together!

Work is the ability to apply a force that moves a body in the direction of that force.

Levers makes work easier by changing: the amount of force. the distance over which the force is exerted. the direction of the force.

1st Class Lever An example of a first-class lever is the joint between the skull and the atlas vertebrae of the spine: the spine is the fulcrum across which muscles lift the head.

2nd Class Lever An example in the human body of a second-class lever is the Achilles tendon, pushing or pulling across the heel of the foot.

3rd Class Lever An example of a third-class lever in the human body is the elbow joint: when lifting a book, the elbow joint is the fulcrum across which the biceps muscle performs the work.

What types of levers are all of these? Third Class Levers

Mechanical advantage is the number of times a lever increases a force exerted on it.

Let’s Practice Name the type of Lever Point to the Fulcrum Point to the Effort Point to the Load

First Class Lever Effort Load Fulcrum

Third Class Lever Effort Load Fulcrum

Second Class Lever Load Effort Fulcrum

Third Class Lever Effort Load Fulcrum

First Class Lever Load Effort Fulcrum

Third Class Lever Fulcrum Effort Load

The End