1. Chapter 4.2 and 4.3 Machines

2. What is a Simple Machine?
A simple machine has few or no moving parts.
Simple machines make work easier

3. Making Work Easier Machines Change the amount of force you exert
Change the distance over which you exert force
Change the direction in which you exert force

4. Total work does not change
Work = Force X Distance
If a machine allows you to apply a smaller force the distance will increase
If a machine reduces the distance the force will increase
If a machine allows you to apply a force in a different direction it doesn’t change how much force you have to apply or how far you move it

5. Work input and output
Work input is the amount of work done on a machine.
Input force x input distance
Work output is the amount of work done by a machine.
Output force x output distance
Din
15 m
Work output is never greater than work input….
FORCE is what changes!!!!!
Dout
3 m
Fin
10 N

6. Mechanical advantage
The number of times a force exerted on a machine is multiplied by the machine
Mechanical ad. = Output force
Input force
If M.A. > 1 machine increases force needed but distance decreases
If M.A. < 1 machine reduces force needed but distance increases

7. Efficiency Efficiency compares the output work to the input work (%)
Cannot be greater than 100%
Efficiency usually < 100%
Friction

8. The 6 Simple Machines Inclined Plane Wheel and Axle Pulley Screw Wedge
Lever

9. Wheels and Axles The wheel and axle are a simple machine
The axle is a rod that goes through the wheel which allows the wheel to turn
Gears are a form of wheels and axles

10. Pulleys Pulley are wheels and axles with a groove around the outside
A pulley needs a rope, chain or belt around the groove to make it do work

11. Inclined Planes
An inclined plane is a flat surface that is higher on one end
Inclined planes make the work of moving things easier
A sloping surface, such as a ramp. An inclined plane can be used to alter the effort and distance involved in doing work, such as lifting loads. The trade-off is that an object must be moved a longer distance than if it was lifted straight up, but less force is needed. You can use this machine to move an object to a lower or higher place.  Inclined planes make the work of moving things easier.  You would need less energy and force to move objects with an inclined plane. 

12. Wedges Two inclined planes joined back to back.
Wedges are used to split things.

13. Screws
A screw is an inclined plane wrapped around a shaft or cylinder.
The inclined plane allows the screw to move itself when rotated.

14. Levers-First Class
In a first class lever the fulcrum is in the middle and the load and effort is on either side
Think of a see-saw

15. Levers-Second Class
In a second class lever the fulcrum is at the end, with the load in the middle
Think of a wheelbarrow

16. Levers-Third Class
In a third class lever the fulcrum is again at the end, but the effort is in the middle
Think of a pair of tweezers

17. Compound Machines
Simple Machines can be put together in different ways to make complex machinery… Compound Machines

18. Rube Goldberg Sample
Sample