1. Mechanical Advantage What do simple machines do for us anyway?

2. There are four ways that a machine helps us to do work.  Transfers our effort force from one place to another. Ex: seesaw  Multiplies your effort force. Ex: crowbar  Magnifies speed and distance. Ex: baseball bat  Changes the direction of the force. Ex: pulley on the flagpole

3. Mechanical Advantage  The number of times a machine multiplies your effort force. Example: If you push on the handle of a car jack with a force of 30 lbs and the jack lifts a 3000 lb car, what is the jack’s mechanical advantage? The jack multiplies your effort force by 100 times.

4. There are 2 types of mechanical advantage.  IMA – Ideal mechanical advantage.  This is the number of times a machine is designed to multiply your effort force.  It is based on measurements of the machine.  Ignores friction  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 friction IMA is always greater than AMA.

5. Lever 1 ft. MA=Fulcrum to Effort / Fulcrum to Load MA=3 / 1 MA=3 3 ft.

6. Solve… 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?

7. Answer… MA = 3 / 0.75 MA = 4

8. Solve… 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 broom is:

9. Answer… MA = 0.3 / 1.2 MA = 0.25

10. Explain… 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.

11. Solve… What is the mechanical advantage of a lever that has an input arm of 3 meters and an output arm of 2 meters?

12. Solve… A lever with an input arm of 2 meters has a mechanical advantage of 4. What is the output arm’s length?