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2 Tutorials that teach Simple Machines: Levers
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Simple Machines: Levers

Simple Machines: Levers

Author: Nathan Lampson
Description:

This lesson will introduce the three types of levers and show how to calculate the mechanical advantage of each. Learn how the application and direction of force increase efficiency with simple machines. Discover how an inclined plane helps exert a mechanical advantage, and how levers are designed around the concepts of input and output forces. Establish engineering skills at the basic level by learning the design of simple machines.

 

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Tutorial

 

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.