1. Chapter 5

2. Machine Can be simple or compound Device that makes work easier by:
Increasing force applied to object (carjack)
Increasing distance over which force is applied (rake)
Changing direction of applied force (ax in wood)
You do work ON a machine and the machine does work on the object

3. 2 forces when a machine is used to do work:
Input force: force applied TO machine = Fin
Output force: force applied BY machine = Fout
Work done on machine = Win
Work done by machine = Wout
Cannot create energy, so Wout is NEVER greater than Win (lost as heat, friction, etc.)
Ideal machine: perfect, no friction, 100% efficient
Win = Wout ***IF Fin is applied over greater distance than the Fout is exerted over (car jack, ramp, crowbar, claw hammer)

4. Mechanical Advantage Ratio of Fout to Fin Calculate: MA = Fout (N)
Fin (N)
Ex: What is the MA of a hammer if the input force is 125N and the output force is 2000N?

5. Efficiency
Measurement of how much work put into a machine is changed into useful output by a machine
Increase efficiency = less heat from friction
Calculate: eff % = Wout (j)
Win (j) x100%
 Real machines always > 100%

6. Simple Machines: Lever
Bar that pivots around a fulcrum
Input & output arms
Fout depends on lengths of input & output arms
3 classes:
1st fulcrum between I and O
Ex: see-saw, scissors
2nd fulcrum at end, I at other
Ex: wheelbarrow
3rd fulcrum at end, I in middle
Ex: tweezers, hockey stick, broom

7. Pulley Grooved wheel with a rope, chain, cable running along
Axle acts as a fulcrum
3 types
Fixed: attached, flag pole
Movable: wheel free, multiples force
Block & Tackle: fixed & movable together

8. Wheel & Axle Inclined Plane
Axle attached to center of larger wheel that rotate together, doorknobs, screwdrivers
Inclined Plane
Sloping surface that reduces amount of force
Fin exerted over a longer distance

9. Screw
Inclined plane wrapped around a post, tiny ramp, jar lids, anything with threads
Wedge
Inclined plane with 1 or 2 sloping sides
Changes direction of Fin
Knife, ax blade