Levers

1) There are 3 classes of levers: 1st, 2nd and 3rd class.

2) To determine the class we ask; "What is in the middle?"

We use the word "please" to help us to remeber the order of the classes.

P (pivot) 1st class
L (lever) 2nd class
E (effort) 3rd class
a
s
e

3) Terminology:

Lever (a long bar or something that acts as a bar with a load, pivot and effort acting on it)

Effort/Force (The energy we apply either by hand or machine.)
Pivot / Fulcrum (The point on the lever where there is rotation.)
Load (A weight that needs to be moved.)

4) The purpose of levers:
a) To apply a force at a distance.
b) To increase the result of the applied effort.
c) To change/affect the direction of an applied force.

5) In a 1st class lever; the closer the pivot is to the load, or the further the effort is applied from the pivot, the stronger that applied force will be.

6) Examples:
Class 1
A worker using a crowbar to lift a heavy rock from the ground.
Effort = Worker presses down on the far end of the bar.
Pivot = Small rock close to the large rock.
Load = The force that is amplified lifts the large rock out of the ground.

Class 2
A person using a door handle to open the door latch.
Effort = The hand turning the handle
Load = The unseen force being applied between the axle and the hand.
Pivot = The axle in the door handle.

Class 3
Broom
A person using a broom to sweep.
Pivot = The person using his top hand as a pivot.
Effort = The person using the hand in the middle of the broom to move the broom.
Load = The increased brushing power and distance of the broom at the cleaning end.