Simple Machines: Levers

A lever is a simple machine consisting of a rigid bar pivoted on a fixed point and used to transmit force, as in raising or moving a weight at one end by pushing down on the other. Force is the amount of effort being applied either by your hand, body weight, or the weight of another object. Force is what is pushing or pulling.

First Class Levers:




Think of two other examples

Second Class Levers:



Or even this



Identify where the Fulcrum, Applied Force, and Load are in this image. (Hint: Do a push up or two to figure it out.)

Third Class Levers:



Explain how a shovel is a third class lever. Be sure to use the words Fulcrum, Force, and Load.

The Law of the Lever

Magnitudes are in equilibrium at distances reciprocally proportional to their weights.(Science) Forces are balanced when the heavier object is closer to the fulcrum and the lighter object is farther away. (English)

The Law of the Lever Explained
Be Calm Kids, The Scary Math Won’t Hurt You!

Force of F1 X Distance from the Fulcrum = Force of F2 X Distance from the Fulcrum


They are balanced because they are equal.


Mechanical Advantage

The mechanical advantage is how much the machine multiplies your force. Basically, how much the machine has helped ease the work.

Mechanical Advantage for Levers = Length of the effort arm / Length of the resistance arm.


To move an object… Distance to be raised x mechanical advantage/distance to be pushed.


Putting It All Together

While driving ever so cautiously home from helping blind, orphaned children learn to read your car is hit by an asteroid. Amazingly, the impact only smashed the trunk causing your car to be pinned in place but otherwise in perfect working condition!You are stuck and must get home to diligently work on your homework for Mr. Evans’ physics class. Just then you notice a large, astonishingly indestructible, board from a local construction site. You place the board under the boulder creating… Some quick estimation and you decide the boulder weighs 600 pounds. Some quick charisma and you convince the extremely strong bodybuilder walking by to help you.

How far are you going to push the board under the boulder to be able to use the lever?!?

How far is the bodybuilder going to have to push down for you to drive off?!?


Will you be able to get home to finish your physics homework?!?

Hint: The bodybuilder can exert up to 150 lbs of force, the board is 10 feet long and you have to lift the boulder 1 foot off the ground to get your car out.
There are multiple answers as long as you can explain them.

Answers
The boulder needs to be raised 1 foot off the ground.
Yay! Your homework does get done!

The moral of the story is…
Even under extreme circumstances your homework should always get done.