LEVERS. ~ Archimedes. Introducing… The Lever. A lever includes a stiff structure (the lever) that rotates around a fixed point called the fulcrum. fulcrum. Lever – A bar that is free to move about a fixed point Parts of a lever Fulcrum – The fixed point of a lever
Can you think of other muscle levers in your body?
What do simple machines do for us anyway?
This is the number of times a machine is designed to multiply your effort force.
It is based on measurements of the machine.
AMA – Actual mechanical advantage
This is the number of times the machine actually multiplies your effort force.
AMA = resistance force/effort force.
Includes the effects of frictionThere are 2 types of mechanical advantage.
IMA is always greater than AMA.
MA=Fulcrum to Effort / Fulcrum to Load
MA=3 / 1
A construction worker uses a board and log as a lever to lift a
heavy rock. If the input arm is 3 meters long and the output arm is 0.75 meters long, what is the mechanical advantage of the lever?
MA = 3 / 0.75
MA = 4
Sometimes levers are used to multiply distance. For a broom, your upper hand is the fulcrum and your lower hand provides the input force.
The mechanical advantage of this
MA = 0.3 / 1.2
MA = 0.25
A mechanical advantage less than one doesn’t mean a machine isn’t useful. It just means that instead of multiplying force, the machine multiplies distance.
A broom doesn’t push the dust with as much force as you use to push the broom, but a small movement of your arm pushes the dust a large distance.
What is the mechanical advantage of a lever that has an input arm of 3 meters and an output arm of 2 meters?
A lever with an input arm of 2 meters has a mechanical advantage of 4. What is the output arm’s length?
2 / x = 4
Solve for x by multiplying both sides by the denominator which is x. You get: 2 = 4x
Divide each side by 4 you get: 2 / 4 which is equal to .5
Input Arm = 2
Output arm = 0
MA = 4