How Did Isaac Newton Discover the Laws of Motion?

By Lauren Farrelly; Updated April 24, 2017

How Did Isaac Newton Discover the Laws of Motion?

Isaac Newton conducting an experiment with a prism

Sir Isaac Newton was a mathematician and physics scholar who transformed our scientific world. In 1666, Sir Isaac Newton developed the theories of gravitation when he was just 23 years old. Then, in 1686, he presented three laws of motion in the "Principia Mathematica Philosophiae Naturalis." It is believed that he first started studying the effects of gravity after watching an apple fall. Why did it fall, and what determined the speed at which it fell? It is believed that this incident, as well as his curiosity for seeing stars and planets above without them falling to the ground, led him to develop the laws of motion.

What are the Laws of Motion?

Newton developed three laws of motion. The first is the definition of inertia: any object will remain at rest or in motion in a straight line unless forced to change by the application of an external force. Objects in motion tend to stay in motion, and objects at rest tend to stay at rest, unless acted upon by an outside force.

The second law explains how the velocity of an object can changes when an additional force is applied. The second law simply states that the force needed to accelerate an object equals the mass of the object multiplied by its acceleration. The formula is: Force = Mass X Acceleration.

The third law states that for every action (or force), there is an equal and opposite reaction. For example, when you stand on something soft, the object caves in or is pushed down. This is the reaction of your force on the soft object, and the soft object's reaction to you standing on it.

Why was Newton's Discovery Important?

We use Newton's Laws of Motion to explain various motions and reactions we observe on Earth and in space. His discoveries were important because they helped define rules of physics and contributed to the development of many modern technologies, including air planes and development of rockets and space ships. His discoveries have also been implemented by physicists for over 300 years, and have become the main theories studies in modern day physics.


About the Author

Lauren Farrelly has been writing and producing for television since 2003. She has experience covering sports, business news and general news events for CNBC, ESPN and Bleacher Report. Farrelly has a BA in broadcast journalism from Arizona State University.