Levers are a form of simple machine where a rigid bar can pivot, or rotate, on a fixed point. The fixed point where a lever pivots is called the fulcrum.
Levers provide a mechanical advantage to a force that is being exerted. The mechanical advantage of a lever can increase the input force that is being applied to the object and change the direction of the force.
There are three types of levers that are classified based on the distance the fulcrum is from the input force.
First-Class Levers
First class levers change the direction of the input force
As long as the fulcrum is closer to the output force, first-class levers increase force.
Examples: pliers, seesaws, scissors
Second-Class Levers
Second class levers don't change the direction of the force being applied, but they do increase force.
Examples: doors, nutcrackers, bottle openers
Third-Class Levers
Third-class levers do not change the direction of the input force, but they increase distance.
Examples: baseball bats, shovels, fishing poles
To calculate the mechanical advantage of a lever, divide the distance from the fulcrum to the input force by the distance form the fulcrum to the output force.
ideal mechanical advantage = distance from fulcrum to input force / distance from fulcrum to output force
Example:
I am using a can opener to open a can of peaches. The fulcrum is 2cm from the output force and 10cm from the input force. What is the ideal mechanical advantage of the lever I am using to open the can of peaches?
distance from fulcrum to input force = 10cm
distance from fulcrum to output force = 2cm
ideal mechanical advantage = distance from fulcrum to input force / distance from fulcrum to output force
ideal mechanical advantage = 10cm / 2cm
ideal mechanical advantage = 5
The output force of the lever is 5 times greater than the input force.
