1. WORK & SIMPLE MACHINES
GRADE 8
GRADE 6

2. WHAT IS WORK? WORK = FORCE X DISTANCE
Joules = newtons (N) X meters (m)

3. CALCULATING WORK -----------------------------------------------
The crane uses 30 newtons of force to lift the iron block 8 meters.
Work done
 = Force x Distance moved
 = 30 newtons (F) x 8 meters (D)
 = 240 Joules
How much work was done?
Because the block is held up high, it becomes:   
potential energy
= 240 J (due to gravity)
If the mass then falls freely to the ground, just before it hits the ground, it’s . . .
240 J of kinetic energy
   

5. Longer Plane = More Distance
INCLINED PLANE
Flat surface with 1 end higher than other
Used to gradually raise or lower objects
EFFICIENCY
Friction reduced if surfaces of plane & load are smooth
MECHANICAL ADVANTAGE (MA)
INPUT FORCE
DISTANCE
Longer Plane = More Distance

6. Examples of INCLINED PLANES

7. Longer Point/Edge = More Distance
WEDGE
Type of inclined plane
Has 1 or 2 sloping sides
Force applied to wide end
Narrow end driven into object– push object apart
EFFICIENCY
Friction reduced if edge sharper
MECHANICAL ADVANTAGE (MA)
INPUT FORCE
DISTANCE
Longer Point/Edge = More Distance

8. Examples of WEDGES

9. More threads = More Distance
SCREW
Type of inclined plane
Wrapped around a rod
Direction of force changed
Amount of force increased
EFFICIENCY
Increased when threads closer
MECHANICAL ADVANTAGE (MA)
INPUT FORCE
DISTANCE
More threads = More Distance

10. Examples of SCREWS

11. LEVER Does work by turning around FULCRUM (fixed point)
Force applied to do the work = EFFORT
Force created by LOAD when trying to move it = RESISTANCE
EFFICIENCY GREATEST WHEN WORK REQUIRES THE LEAST EFFORT

12. Longer Effort Arm = More Distance
MECHANICAL ADVANTAGE (MA)
INPUT FORCE
DISTANCE
Longer Effort Arm = More Distance
effort arm
load
effort
fulcrum

13. LESS EFFORT NEEDED TO DO THE WORK
LESS DISTANCE BETWEEN LOAD & FULCRUM
LESS EFFORT NEEDED TO DO THE WORK

14. TYPES OF LEVERS

15. Turning larger wheel = More Distance
WHEEL & AXLE
Large wheel fixed to smaller wheel (or shaft) called an axle
Both turn together
Effort usually on larger wheel, moving load of axle
MECHANICAL ADVANTAGE (MA)
INPUT FORCE
DISTANCE
Turning larger wheel = More Distance

16. Think of as lever rotating in circle around center fulcrum
Like steering wheel (larger wheel) on column (axle)
Wheel & axle turn together
EFFICIENCY:
Reduced friction with lubricant

17. HOW DOES WHEEL & AXLE WORK?

18. Rope around more wheels = More Distance
PULLEY
Wheel with groove
Allows rope to ride on wheel without slipping off
MECHANICAL ADVANTAGE (MA)
INPUT FORCE
DISTANCE
Rope around more wheels = More Distance

19. TYPES OF PULLEYS FIXED PULLEY (like clothesline or flagpole)
Pulley stays in one position
Moves LOAD up, down or sideways
Changes DIRECTION of force
Does not reduce EFFORT

20. TYPES OF PULLEYS MOVABLE PULLEY Moves along with LOAD Reduces EFFORT
(for lifting or lowering heavy objects)
Moves along with LOAD
Reduces EFFORT
Increases DISTANCE

21. Examples of PULLEYS

22. GEARS Wheels with teeth, so one turns the next
SMALLER gear turns FASTER than larger gear
One gear makes other gear beside it turn in OPPOSITE DIRECTION
Speeds things up,slows them down, changes direction of force
GEARS

23. Compound machines are made of 2 or more simple machines.

24. Rube Goldberg Machine
An over engineered machine that performs a very simple task in a very complex fashion, usually including a chain reaction.