| A | B |
|---|
| equilibrium | all the forces acting on it balance one another |
| Newton's First Law | unless a net force acts on an object, the object will remain in constant motion and an object at rest stays at rest until a net force acts on it |
| inertia | tendency of an object at rest stays at rest until a net force acts on it |
| effort | an applied force against inertia |
| Newton's Second Law | describes how acceleration, mass, and net forces are related |
| acceleration | the rate at which the velocity of an object changes over time |
| Newton's Third Law | states that when one object exerts a force on a second object, the second object exerts a force on the first object |
| machine | a device that changes the direction or the amount of force needed to do work |
| simple machine | a machine that only has a few parts and makes work easier |
| pulley | a wheel with a grooved rim in which a rope can run to change the direction of the pull and so lift a load |
| fixed pulley | a pulley attached in a position above a load to be lifted |
| movable pulley | a pulley attached to a load that is being lifted |
| wheel and axle | a simple machine consisting of a large circular object rigidly secured to a small circular object or shaft |
| lever | a rigid bar that rotates around a fixed point called the fulcrum |
| load | the weight of an object you are moving |
| fulcrum | the point at which a level pivots |
| inclined plane | a flat surface with one end higher than the other |
| screw | a smooth metal rod with a tiny inclined plane wrapped around it |
| pitch | the distance between two threads of a screw |
| wedge | two inclined planes back to back against each other |
| complex/compound machine | a machine that uses two or more simple machines |
