In addition to his vast contributions to the fields of mathematics, Newton is also credited with the development of many topics in, among other things, philosophy, astronomy, and physics. You may have heard of Newton's Laws of Motion, in particular his first and third laws (paraphrased below).
First Law: an object in motion stays in motion, and an object at rest stays at rest unless and external forces acts upon it.
Second Law: The equation F = ma, where m is the mass of the object, F is the net force, and a is the acceleration.
Third Law: for every action there is an equal and opposite reaction.
Let's take a closer look at Newton's First Law. It states that "an object in motion, stays in motion."
Consider this example: Hold a bouncy ball waist high and then drop it. What happens to the ball?
When you drop it, the ball is in motion - but does it stay in motion? Of course not, we know that eventually the ball will stop bouncing. Does this mean Newton's First Law is incorrect?
Of course not! Read the last part of the law... "Unless and external force acts upon it."
Now I know that YOU did not act upon the ball, but another external force did. Guess what that force was? Yup, that's right - Gravity! Gravity pulls the ball back down to earth, eventually making it stop.