Forces and motion is the branch of physics that explains why things move (or stay still), why they speed up or slow down, and why they go in straight lines or curves. A force is simply a push or a pull. Forces are everywhere: gravity pulls a ball to the ground, friction stops a sliding box, a magnet pulls iron, your foot pushes a football. The English scientist Isaac Newton worked out the most important rules of motion over 300 years ago, and they still describe almost every everyday movement perfectly.
- What a force isA push or a pullMeasured in newtons (N)
- Newtons 1st lawInertiaThings keep going unless pushed
- Newtons 2nd lawF = m x aForce = mass times acceleration
- Newtons 3rd lawAction + reactionEqual and opposite pairs
- Earths gravity9.8 m/s2Pulls everything towards the ground
- Most common forceFrictionSlows almost every motion
What you will learn here
- What is a force: pushes, pulls and how forces are measured.
- Newtons three laws of motion: the rules that govern almost all everyday motion.
- Speed, velocity and acceleration: how scientists measure movement.
- Friction: the force that resists sliding.
- Air resistance: the friction of moving through gas.
- Momentum: the mass-times-velocity that makes things hard to stop.
- Centripetal force: the pull that keeps things going in circles.
Why this matters
Forces and motion are the basis of almost all engineering. Cars, bridges, planes, rockets, roller coasters, footballs, bicycles and even our own walking depend on the laws Newton worked out. Knowing these rules lets engineers design things that move safely and efficiently, and lets us predict how new things will behave before we build them. From bouncing a ball to launching a satellite, the physics is the same.