1. Simple Machines

2. Simple machines convert potential energy into kinetic energy.
Simple machines change the direction and/or the magnitude of a force.
Simple machines help humans apply force over great distances.
Simple machines are critical to technology and human existence.

3. Simple machines create “mechanical advantage”
MA = Force out divided by Force in

4. Simple machines are also created to work at maximum efficiency (100%)
Efficiency= Work out divided by Work in

5. Examples of Simple Machines:
Levers:
Linear device with a pivot point or fulcrum
baseball bat
crowbar
stapler
bottle opener

6. Now…the lever
Three parts of the lever - Fulcrum (pivot point), the effort force, and the resistance force.
Effort force is the force YOU PUSH ON
Resistance force is where the RESISTANCE IS COMING FROM

7. Calculating M.A. For levers: (fulcrum between force and load)
Distance from fulcrum to force divided by distance from fulcrum to load
(fulcrum at fixed end)
Distance total divided by distance to load or force (which ever shows first)

8. First class lever

9. Second Class Lever

10. Third Class Lever

11. Mechanical Advantage
Mechanical Advantage for ALL THREE LEVERS are the same.

12. More examples: Wheel and Axle:
Reduces friction in order to max out work
car wheels
train wheels
conveyor belts
pulley systems

13. First, the wheel and axel
Simple Machine = Diameter of the wheel divided by the diameter of the axle
What is the mechanical advantage of a tractor with a wheel diameter of 1 meter divided by an axle with a diameter of 7 cm?

14. Pulley
M.A. of the pulley is simply the number of ropes in between the pulleys.
Do not count the rope you are pulling on, just count the rest of the ropes
OR count the number of turns the rope makes between the load and the force

17. Still more examples: Inclined planes or wedges
Exchanges increased distance for less power
“switch back roads”
screw
ramp
axes
scissors

18. To calculate mechanical advantage:
For ramps:
length divided by the height

20. Example 1:
The UPS guy can lift a package from the ground to his truck using 950N of force. However, he decides to use a near by ramp and only exerts a 350N force. What is the mechanical advantage of the ramp?

21. Example 2:
The efficiency of a squeaky pulley system is 73%. The pulleys are used to raise a 58kg object 3.00m. If the rope is pulled 18m by a worker, how much force was he exerting?