Newton's First Law (The Law of Inertia):
An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
This means that there is a natural tendency of objects to keep on doing what they're doing. All objects resist changes in their state of motion. In the absence of an unbalanced force, an object in motion will maintain this state of motion.
Example: A person not wearing a seatbelt flies through a car window when someone slams on the breaks because the person's body wants to remain in continuous motion even when the car stops.
Newton's Second Law
Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
However, the Second Law gives us an exact relationship between force, mass, and acceleration. It can be expressed as a mathematical equation:
F = ma
FORCE = MASS times ACCELERATION
Example:Two students are in a baseball game. The first student hits a ball very hard and it has a greater acceleration than the second student who bunts the ball lightly.
Newton's Third Law
For every action there is an equal and opposite re-action.This means that for every force there is a reaction force that is equal in size, but opposite in direction. That is to say that whenever an object pushes another object it gets pushed back in the opposite direction equally hard.
Example: The rocket's action is to push down on the ground with the force of its powerful engines, and the reaction is that the ground pushes the rocket upwards with an equal force.