Accelix

Meet Accelix, a rocket skateboard who speeds up by the same amount every second.

Acceleration is the rate at which velocity changes. When the acceleration stays constant, the velocity changes by the same amount in each second, and the final velocity is simply the starting velocity plus the acceleration multiplied by the time, v = u + at.

Start from rest, so u = 0, and accelerate at 3 m/s² for 5 s. The final velocity is v = 0 + 3 × 5 = 15 m/s. After 10 s it would be 30 m/s. On a graph of velocity against time, the motion is a straight line whose slope is the acceleration.

The same equation works for slowing down. A negative acceleration makes the velocity fall by the same amount each second until the object stops.

Objects falling freely near Earth's surface are a natural example. If air resistance is small, their speed grows by about 9.8 m/s every second.