1. Bell Work: Simple machines 1. Simple machines make work ( easier / harder ). Match the tool to the type: Type of machineTool 2. Incline planeDoor knob 3. Wheel and axelFlag pole 4. LeverRamp 5. PulleyCrow bar

2. Machines

3.  A machine is a device that makes work easier.  Examples: hammer, bicycle ramp, scissors, shovel, and doorknob

4. Machines  Machines can do a variety of jobs: pump water from a well, hoist a sail, plow a field, catch a fish.  Machines make work easier by changing the size or direction of the applied force.

5. Two forces involved in using a machine 1. The force applied to a machine is the effort force (F in )  Example: when you pull down on the handle of a crowbar, you are applying an effort force.

6. Two forces… 2. The force applied by the machine is the resistance force (F out )  Example: Motor turns fan

7. Work Input 

8. Output 

9. What do machines do??  Machines make work easier, but do not multiply work.  So, work output can never be greater than work input

10. Mechanical Advantage 

11. Ideal Mechanical Advantage 

12. Efficiency 

13. Types of Simple Machines I. Inclined Plane – a slanted surface used to raise an object. Example: a ramp  Wedges and Screws – wedge is an inclined plane that moves. Have an edge that is thinner at one end. Examples: knife, ax, wedge  A screw is also an inclined plane. It is an inclined plane wrapped around a cylinder to form a spiral.

14. Simple Machines II. Levers – a bar that is free to pivot a fixed point when an effort force is applied. The fixed point of the pivot is called the fulcrum.

15. Levers ****Three classes of levers: 1. Fulcrum is between the effort force and the resistance force. Example: crowbar, pliers, scissors and seesaws  Resistance force is between fulcrum and effort force. Examples: wheelbarrows, doors  Effort force is greater than the resistance force and the fulcrum

16. Simple machines III. Pulleys – a chain, belt, or rope wrapped around a wheel. A pulley can change either the direction or the amount of an effort force. IV. Wheel and Axle – a lever that rotates in a circle. Made of 2 wheels of different sizes. Examples: bicycles, Ferris wheels, water wheels and gears.