How To 

Understanding Newton’s Laws


Sir Issac Newton was one heck of a thinker. He dabbled in physics, mathematics, astronomy, and many other fields. We can even thank him for inventing calculus! But of all Newton’s discoveries, his laws of motion just might be the most important. They became the key ideas we use to understand the workings of the universe. Here’s what Newton’s Laws of Motion are all about.


1. Every object in motion will remain in motion unless acted upon by an external force.
The same goes for objects at rest. If a ball is sitting on the ground and not moving, it will not move until something pushes it (external force). If the ball is moving, it will continue to move at the same speed and in the same direction until an external force changes the speed or direction (or both). This is assuming that there is nothing inhibiting motion, such as friction. This concept can be applied to space: if we send out a probe, it will keep going on forever in a straight line and the same speed until the path is altered by another force, such as gravity from a nearby planet.


2. Force is equal to mass times acceleration.
You’ve definitely heard this one before, but hearing it and understanding it are two different things. Written as the formula F=ma, this law states that acceleration, mass, and magnitude of force are all related. When one changes, the others change. For example, if you have a baseball and a bowling ball and you push both with the same amount of force, the baseball’s acceleration will be higher than the bowling ball’s because the bowling ball has more mass.


3. For every action, there is an equal and opposite reaction.
Everything seeks balance, even forces. For every push, there is a pull. For every type of force, there is an equal and opposite force to balance it out. You experience this every day. When you sit on a chair, you’re applying force downward. At the same time, the chair is applying force upward. Otherwise you’d crash right to the floor! As another example, if you were to shoot a gun, you’d feel the kickback because the force that sends the bullet out one end has an equal force that pushes the gun in the other direction.