Newton's Laws of Motion Made Easy

Sir Isaac Newton formulated the three elementary laws of motion.
••• Images

Sir Isaac Newton is considered by many to be the father of modern physics. He postulated a number of natural laws, the most famous of which is gravity, when he was supposedly hit in the head by a falling apple. It is his laws of motion, though, that can be confusing for some people. However, once they're broken down, they become relatively easy to understand.

Newton's Laws of Motion

There are three laws of motion, according to Newton. The first is, "Every object in a state of uniform motion tends to stay in that state of motion unless an external force is applied to it." The second law is, "The relationship between an object's mass M and acceleration A, and the applied force F is F=MA. Acceleration and force are vectors, and in this case the direction of the force vector is the same as the direction of the acceleration vector." And the third law is, "For every action there is an equal and opposite reaction."

First Law

Objects in motion tend to stay in motion. This is the simplest of Newton's laws, and is usually referred to as inertia. Inertia means that once an object starts in a certain direction, it requires an equal or greater force to stop it from moving. If a car is driving in a certain direction, than it will take an equal or greater force than the car to stop its motion, such as a car moving in the opposite direction with the same force.

Second Law

Broken down into more common language, an object's force is the combination of its mass and acceleration. The law also states that acceleration and force must be in the same direction in order for the formula to work. For example, a bullet is stationary until the trigger is pulled and the gunpowder explodes. The power of the explosion is the acceleration (A), and the weight of the bullet is the mass (M). The force of the bullet (F) is measured as the mass times its acceleration, and can be said to be the impact that the bullet will strike with.

Third Law

Everyone has heard the wisdom that for every action there is an equal and opposite reaction. The easiest way to see this law in action is to step off of a boat. The force that the person uses to push himself forward ends up pushing the boat backward in an equal, yet opposite manner.


Newton's three Laws of Motion are the cornerstones of physics, so you need to know and understand these laws to understand the more complicated aspects of physics.

Related Articles

Newton's Laws of Motion
What Is the Difference Between Newton's First Law of...
What is Inertia?
What Are Some Examples of the Laws of Motion?
How To Demonstrate Newton's Laws of Motion
How the Mass of an Object Affects Its Motion
How to Find the Inertia of an Object
How to Calculate Inertial Force of Mass
How Did Isaac Newton Discover the Laws of Motion?
What is the Relationship Between Force Mass And Acceleration?
How to Calculate a Change in Momentum
How to Calculate Tangential Force
How to Calculate Brake Torque
How to Calculate Pendulum Force
How are Force And Motion Related?
The Physics of a Playground Slide
How to Calculate Force
How Does Newton's Laws of Motion Interact With Tennis?
Types of Newton Scooters