1. Simple Machines
Machine: an object that changes either the magnitude or direction of a force

2. Simple Machines There are six simple machines: lever inclined plane
wedge
wheel & axle
pulley
screw
All other machines are made out of simple machines.
Machines make life easier.
Without simple machines there would be no other machines.

3. Mechanical Advantage (how machines make life easier)
Double a force by using a machine
with a mechanical advantage of two!
effort force (Fe): the force exerted on a machine
resistance force (Fr): the force exerted by a machine

4. Efficiency Wi = Fede Wo = Frdr
Work is input (Wi) to a machine when an effort force (Fe)
is applied over a distance (de).
Wi = Fede
Work is output (Wo) from a machine when it exerts a resistance force (Fr) over a distance (dr).
Wo = Frdr

5. Ideal Machines (perfect machines)
input work (Wi) = output work (Wo)
efficiency = 100%
Ideal Mechanical Advantage
No real machine is perfectly efficient!

6. Lever (a rigid object pivoting on a fulcrum)
Three types of levers:
1st class lever: fulcrum between Fe & the load
2nd class lever: the load between Fe & the fulcrum
3rd class lever: Fe between the load & the fulcrum Fe
load Fr Fe
load Fr
load Fr Fe
1st class lever 2nd class lever rd class lever

7. Lever Examples

8. Crowbar (1st Class Lever Example)Fe Fr

9. Wheel & Axle
Wheels rotate around an axle.

10. Wheel Examples

11. Well Wheel Fe Fr

12. A pulley is a wheel with a rope running over it

13. Pulley Examples

14. Inclined Plane A slanted surface or ramp
Reduces the force required to move objects

15. Inclined Plane Examples

16. Wedge A wedge is usually a triangle shape with a sharp point.
A wedge is used to split, secure, or lift.
Applying a force to one end pushes the wedge between something
The pictured wedge is designed to split wood when hit with a sledge hammer

17. Wedge Examples Wedges that split: teeth knives zippers
Wedges that secure:
doorstops
nails
Wedges that lift:
shims
golf wedges

18. Screw (a helical inclined plane)
A screw is an inclined plane twisted around an axis.

19. Screw Examples

20. All 6 Simple Machines Lever Inclined Plane Wheel & Axle Screw Pulley
Wedge

21. Compound Machine: two or more linked simple machines
Compound Machines
Link to Rube Goldberg video from online. I downloaded one and inserted it into my presentation, but I can’t post that.
Compound Machine: two or more linked simple machines
The mechanical advantage of a compound machine is the product of the component simple machines’ mechanical advantages.

22. Notes:

23. Chapter 10 Practice Problems (p. 238): 13-16
Your Turn
Chapter 10 Practice Problems (p. 238): 13-16