Forces and Motion
A force is a pushing or pulling action that can make things move, change direction, or change shape. It's hard to believe, but everything in the world is in motion, all the time. Even things that look perfectly still are packed with atoms that are vibrating with energy. Understanding how motion works was one of the great milestones of science and it's credited to the brilliant English physicist Sir Isaac Newton. His laws of motion, written over 300 years ago, were so well stated that scientists still use them in most situations today. The basic idea Newton taught us is that motion is caused by forces—which is easy enough to understand: kick a ball (the force) and it flies into the air (the motion). But forces don't always make things move: a bridge has lots of forces acting on it, but it doesn't go anywhere. Also, the "motion" forces produce is sometimes a shift in the direction in which something is moving or a change in its shape. So what exactly are forces and how they do they produce these different kinds of motion? It's time to take a closer look at the science of moving things.