1. -a machine that does work with one movement
Simple Machines
-a machine that does work with one movement

2. Levers A bar that is free to pivot, or turn, about a fixed point
Fulcrum- fixed point on the lever
Input arm- part of lever that person adds input force to
Output arm- part of lever that moves the output force or work

3. 3 types of Levers

4. First class lever
Fulcrum is located between the input force and the output force
screwdriver opening paint can
HW: 5 1st class levers

5. Second class lever
Ouput force is located between the input force and the fulcrum
Wheel barrow
Output force
fulcrum
Input force

6. Third class lever
Input force is located between the output force and the fulcrum
Baseball bat, rake, hockey stick
fulcrum
Output arm
Input arm

7. Pulleys
Grooved wheel with a rope, chain, or cable running through the groove
Fixed pulleys
Change direction of force
Gravity Help!

8. Movable Pulleys Move when a force is applied.
Multiply the input force 2x.

9. Pulley Systems Block and Tackle
A system of fixed and movable pulleys
MA = number of ropes supporting the weight
Do not count rope that you pull down on.
Do count a rope that you pull up on.
Pulley Systems Block and Tackle

10. MA of pulleys!
120 N
120 N
120 N
120 N

11. Wheel and Axle Two wheels of different sizes that rotate together
Can you think of any?
Doorknobs
Faucets
Steering wheel
Stereo volume knobs

12. Inclined Planes
A sloping surface that reduces the amount of force needed to do work
Ramps
Roads

13. Screw Inclined plane wrapped around a cylindrical post Wood screws
Soda lids
Olive jars

14. Wedge
Inclined plane with one or two sloping sides that moves through an object or material to change the direction of the force.
Knives
Axes
Fullbacks

15. Complex Machines
Two or more simple machines working together to perform a task
Scissors
Faucets
Bicycles

16. Efficiency Ability of a machine to use all of the work in.
E = output work/input work x 100%
Efficiency is reduced by friction.
Therefore always less than 100%

17. Machines: Big Ideas
Change the way a person does work, not how much work is done.
Have:
Input work- effort put in
Output work- the work done by the machine
No machine can create work
Input work always greater than output work.
Due to friction

18. Big Ideas contd. Multiply input/our force Multiply input distance
Screwdriver opening a paint can, wheel barrow
Multiply input distance
Rake, hockey stick
Change the direction of the input force.
Pulley

19. Efficiency calculations
How efficient is a pulley system that requires 200J of input work to produce 150 J of output work?
What is the efficiency of a lever that requires 100 N of input force for 5 m? The work completed to move the bail of hay is 400 J.

20. The End
Calculations are next!

21. Calculations
Calculate the Mechanical Advantage of a lever that has an input arm of 15 meters and a output arm of 3 meters.
15 m
3 m
fulcrum

22. MA of levers MA = length of input arm length of output arm = 15 m 3 m
= 5

23. MA of a Wheel and axle
Calculate the MA of the door knob that you turn as you try to sneak into Mr. Miller’s room tardy.
The knob itself has a radius of 12 cm and the axle that runs through the knob as a radius of 1.2 cm.

24. MA of W&A = radius of wheel
radius of axle
= 12 cm
1.2 cm
= 10

25. MA of an Inclined Plane
Calculate the mechanical advantage of an inclined plane/ramp used to load your ATV onto the bed of a truck.
The truck’s bed is exactly 2 meters off the ground and the ramp is 8 meters long.

26. MA of I.P. = length of ramp height of ramp
MA = 8 m
2 m = 4
8 m
2 m