1. Advanced Physical Science Ms. Pollock 2010 - 2011
Machines
Advanced Physical Science
Ms. Pollock

2. What is a machine? Machine – device that makes doing work easier
Does not have to be complex
Can increase force applied to object
Can increase distance over which force is applied

3. What is a machine?

4. Input and Output Force
Two forces involved when machines used to do work
Input force – force applied to machine
Output force – force applied by machine
Machines MUST conserve energy. It cannot be gained or lost.
Output work will always be less than input work.

5. Input and Output Forces

6. Ideal Machines
If there were no friction, no energy would be converted to heat. Work input would equal work output.
Ideal machines can “increase” the amount of force that is output.

7. Mechanical Advantage Ratio of output force to input force MA = Fout
Fin
Ideal mechanical advantage ignores friction

8. Efficiency
How much work put into a machine is changed into useful output work
Efficiency = Wout X 100 %
Win
Lubricant added to reduce friction and increase efficiency

9. Simple Machines Machine that does work in only one movement Six types
Lever
Pulley
Wheel and Axle
Inclined Plane
Screw
Wedge

10. Simple Machines

11. Levers Bar that is free to pivot around a fixed point
Fixed point – fulcrum
Output force dependent of lengths of input arm and output arm
Three classes of levers

12. Levers

13. Levers First Class Second Class Third Class
Fulcrum between input and output forces
Screwdriver opening paint can
Second Class
Output force located between fulcrum and input force
wheelbarrow
Third Class
Input force between output force and fulcrum
Bat hitting ball

14. Levers

15. IMA of a Lever IMA = length of input arm length of output arm
IMA = Lin
Lout

16. Pulleys Grooved wheel with rope, chain, or cable running along groove
Two types
Fixed
Changes only direction of force
Movable
Reduces force needed to move object

17. Pulleys

18. Fixed Pulleys
Attached to something that does not move
IMA = 1

19. Movable Pulleys
End of rope fixed, wheel free to move

20. Block and Tackle
System of fixed and moveable pulleys

21. Wheel and Axle Shaft or axle attached to center of larger wheel
Rotate together
IMA= radius of wheel
radius of axle
Gear – wheel and axle with teeth around outside edges

22. Wheel and Axle

23. Inclined Planes
A sloping surface that reduces the amount of force required to do work
IMA = length
height
Spreads force out over greater distance

24. Inclined Plane

25. The Screw Inclined plane wrapped in spiral around cylindrical post
Modified inclined plane

26. The Wedge
Inclined plane that moves through an object or material

27. Compound Machines
Two or more simple machines that operate together

28. Challenge
List EVERY simple machine you can think of that you have PERSONALLY USED today.
The person with the most LEGITIMATE answers wins.