1. Simple Machines and Mechanical Advantage
Machine– is an instrument that makes work EASIER.

2. Rube Goldberg Creations
Passing man (A) slips on banana peel (B) causing him to fall on rake (C). As handle of rake rises it throws horseshoe (D) onto rope (E) which sags, thereby tilting sprinkling can (F). Water (G) saturates mop (H). Pickle terrier (I) thinks it is raining, gets up to run into house and upsets sign (J) throwing it against non-tipping cigar ash receiver (K) which causes it to swing back and forth and swish the mop against window pane, wiping it clean. If man breaks his neck by fall move away before cop arrives.

3. Rube Goldberg

4. Honda Commercial

5. Simple Machines and Work
2 types of work involved with machines:
1. Work input– the work that goes INTO the machine
WORK INPUT = Effort Force X Effort Distance
Effort Force is the force applied TO the machine. (usually what YOU apply to the machine)
Effort Distance is the distance over which you apply force.

6. Simple Machines and Work
2. Work Output– the work done by the MACHINE
WORK OUTPUT = Resistance Force X Resistance Distance
Resistance Force is usually the weight of the object being moved.
Resistance Distance is the distance the object is moved EVEN if there was no machine.

7. IMPORTANT!
Machines DO NOT INCREASE the work put into them, they just make work easier.
Allows you to use
less force!!!

8. Mechanical Advantage
Mechanical Advantage: how many times the machine multiplies your effort force.
how much the machine REDUCES how much effort force you have to apply.
What you lose in EFFORT FORCE, you gain in EFFORT DISTANCE.

9. Mechanical Advantage Example:
If you are using a machine that has a mechanical advantage of 2.5,you will have increased your EFFORT DISTANCE by 2.5 times.
This allows you to REDUCE the EFFORT FORCE needed by 2.5 times.

10. Mechanical Advantage Ideal Mechanical Advantage (IMA)=
Assumes that there is NO FRICTION involved.
IMA = Effort Distance/ Resistance Distance or
Resistance Force/ Effort Force
Ed / Rd or Rf / Ef

11. 6 Types of Simple Machines
Inclined Plane
Wedge
Screw
Lever
Wheel and Axle
Pulley
All are forms of
inclined planes

12. Inclined Plane A flat slanted surface Ef Rf Rd Ed
The weight of the box is the Rf

13. Inclined Plane IMA Box weighs 3 meters 250 N 1.5 meter Ed
IMA = Ed / Rd 3m / 1.5m = 2 or
IMA = Rf / Ef / ??? = Rf
IMA Rd
IMA Ef
Box weighs
250 N
3 meters
1.5 meter

14. Inclined Plane and Work
Work = Force X Distance
Use either: Resistance Force and Resistance Distance OR
Effort Force and Effort Distance
Box weighs
250 N
3 meters
1.5 meter
Work = Rf x Rd N X 1.5m = 375 Joules

15. Wedge A moving inclined plane The longer and thinner the
Wedge (inclined plane), the higher
The IMA. (the better the machine)

16. IMA of a Wedge A wedge is 2 inclined Planes together. 10/6 = 1.67
6 cm
6 cm
A wedge is 2 inclined
Planes together.
10/6 = 1.67
_______
3.34
Ed/ Rd
10 cm
10 cm
Calculate the IMA of each
Inclined plane and add together.
IMA is 3.34

17. Screw
An inclined plane wrapped around a central bar to form a spiral

18. IMA of a Screw
Higher IMA, MORE THREADS
Lower IMA, less threads
With more threads, turn the screw for a LONGER DISTANCE so can
use LESS FORCE.

19. Lever Rigid bar that is free to pivot about a fixed point.
Fulcrum: the fixed point on a lever.

20. Classes of Levers 1st Class F 2nd Class R 3rd Class E
force Rf
________ Rf
1st Class F
2nd Class R
3rd Class E
force
_______ Rf
force
_______
Effort DISTANCE = Effort ARM
from the fulcrum to the point of Effort force.
Resistance DISTANCE = Resistance ARM
From the FULCRUM to the point of Resistance force

21. 1st Class Lever Ef Ef Ef Rf Rf Rf
Changes direction of the force

22. 2nd Class Lever Rf Ef

23. 3rd Class Lever Does not multiply your
effort force, It just makes it a
little easier (or increases
speed)

24. Levers and IMA What is the IMA of the following lever?
What kind of lever is it?
.25 m Ef
2 m
300 N

25. Levers and IMA What is the IMA of the hockey stick?
What type of lever is the hockey stick?
Ef = 60 N
. 5 m
2.5 m Rf

26. Wheel and Axle Made up of 2 circular objects of different sizes
Wheel– the large circle
Effort distance
Axle– the smaller circle.
Resistance Distance

27. Wheel and Axle

28. Wheel and Axle and IMA
What is the IMA?
Ed/Rd
6 cm
24 cm

29. Pulley
A rope, belt or chain wrapped around a
grooved wheel.

30. Type of Pulleys Fixed Pulley: pulley attached to a structure.
Changes the direction of the Effort Force
DOES NOT multiply your effort force
Calculate IMA by counting the
number of SUPPORTING ropes.
IMA = 1

31. Types of Pulleys Movable Pulley: attach pulley to a moving object
Multiplies force, but does not change direction
IMA = 2

32. Combination fixed and movable pulleys
Compound Pulleys
Combination fixed and movable pulleys
IMA =
IMA =

33. Examples of Pulleys

34. Examples

35. Block and Tackle System

36. I guess that’s It! Whew!
Any Questions?