1. Physical Science Chapter 12

2.  devices that change the direction of a force or the size of a force that help us to do work  machines will multiply your force OR change the direction of your force  BUT CANNOT DO BOTH (can’t do work for you)

3.  2 forces involved in the use of a machine:  effort force (input)- force applied to the machine  resistance force (output) force opposing the effort force  often equal to weight of object work input is ALWAYS > work output WHY? friction

4.  simple machine- machine that has only 1 or 2 parts  6 simple machines: 1. lever- bar that pivots, or turns, on a fixed point 3 parts: a. effort arm- (input)- end of the bar you push on b. resistance arm (output)- end of bar that pushes on object you want to move c. fulcrum- point at which it pivots

5. A. first class lever-effort arm on one side, resistance arm on other, fulcrum in middle ex: see saw

6.  fulcrum is at one end, EA at the other, RA in the middle  ex: wheelbarrow

7.  fulcrum at one end, RA at the other, and EA in the middle  ex: tweezers, forearm

9.  consists of a lever connected to a shaft  lever usually shaped like a knob or wheel  effort arm- radius of wheel  resistance arm- radius of axle to be considered W&A, BOTH wheel and axle MUST move

11.  consists of a wheel FREE TO SPIN on its axle  lever rotates around a FIXED POINT  2 FXNS:  changes direction of force  provides mechanical advantage (multiplies your force)

12. a. fixed pulley- attached to something that doesn’t move used to change the direction of force doesn’t multiply force at all

13. B. movable pulley- attached to an object being moved multiplies force

14. BLOCK & TACKLE- when fixed & movable pulleys are used together multiplies A LOT of force used to lift car engines, etc

16.  consists of a flat, sloping surface  simplest of all machines  used to move objects from 1 level to another

18.  used to push objects apart  inclined plane that moves  multiplies force and brings it to a single point

20.  inclined plane wrapped around a cylinder  multiplies force  how much it increases force depends on PITCH  pitch- how far apart the threads are  smaller the pitch, the more force it multiplies

22.  2 or more simple machines put together to do work  ex: ax, scissors

23.  # of times a machine multiplies force  MA = resistance force effort force the greater the number, the less work you have to do all machines have a MA

24.  MA of pulley is equal to the number of rope segments pulling up the resistance force