Everything that moves follows three simple rules.
Speed, acceleration and Newton’s three laws, explained with a race car, a rocket and a lot of arrows.
Newton’s three laws in 20 seconds
A short video explaining one idea from the chapter, with every fact checked against the textbook.
The big ideas
Six facts to remember for the test.
Speed
How far you go in a unit of time. Its SI unit is metres per second.
speed = distance ÷ timeVelocity
Speed in a given direction. Running a lap and ending where you started means zero displacement.
velocity = displacement ÷ timeAcceleration
How fast velocity changes. Slowing down is negative acceleration, also called retardation.
a = (v − u) ÷ tFirst law
An object stays still, or keeps moving at the same speed in a straight line, unless a force acts on it. This is inertia.
Second law
Force equals mass times acceleration. The same push moves a light cart faster than a heavy one.
F = m × aThird law
Every action has an equal and opposite reaction, acting on a different object: gas goes down, the rocket goes up.
Try it: the speed calculator
Move the sliders. Speed = distance ÷ time.
Quick quiz
Four questions. Tap an answer to check it.
Revise it as a race
Newton’s Grand Prix stops at every pit stop for a study card and three questions from this chapter. Right answers are nitro boosts.
Play Newton’s Grand Prix