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Speed - the rate at which an object moves

Velocity - speed in a particular direction

Acceleration - the rate at which velocity changes

Force - anything that tends to change the state of rest or motion of an object

Law of motion - law of inertia, law of motion, momentum

Law of inertia - an object at rest will stay at rest until a force acts upon it, and an object in motion will stay in motion at a constant speed in a straight line until a force acts upon it

• Objects moving on Earth eventually slow down and stop because of the forces of friction and gravity

• Ex; a bullet would continue its forward motion in a straight line, but friction from the air slows it down and the force of gravity pulls it toward the ground

Law of motion (acceleration) - the acceleration of an object depends on its mass and the force acting upon it.

• the greater the force, the greater the acceleration

• the more massive the object, the more force it takes to accelerate it

• if a constant force acts upon an object, the object will move with constant acceleration in the direction of the force

• Ex; this is why truck engines are more powerful than car engines. it takes more force to accelerate an object with more mass (a truck), than an object with less mass (a car)

Momentum - the amount of energy that a moving object has (depends on the mass of the object and its velocity); an object’s mass multiplied by its velocity (Ma x Ve = Mo)

Law of conservation of momentum - when an object is given a certain amount of momentum in a particular direction, some other object must receive an equal momentum in the opposite direction

• Ex; when a bullet is fired out of a gun, the bullet’s forward momentum causes the gun to recoil (go backward)