| A | B |
|---|
| screw | looks like a nail with ridges on it |
| thread | the ridges on a screw |
| force | a push or a pull |
| complicated machines | machines with many moving parts |
| simple machines | machines with few moving parts |
| work | use force to move an object |
| fulcrum | the object a lever rests on |
| lever | a stiff bar used to move objects |
| load | an object you want to move |
| first-class lever | has fulcrum between load and force |
| second-class lever | load is between fulcrum and force |
| third-class lever | force is between fulcrum and load |
| axle | bar that goes through center of wheel |
| friction | force caused when 2 objects rub |
| machine | a tool that makes work easier |
| pulley | a wheel with a rope looped around it |
| inclined plane | a sloping surface |
| wedge | thin at one end, thick at other end |
| gear | wheel with bumps around its edge |
| wheel | round object that turns on an axle |
| gravity | force that pulls toward the earth |
| compound pulley | 2 or more pulleys working together |
| fixed pulley | a pulley; stays attached in one place |
| moveable pulley | a pulley that is attached to a load |
