Acceleration: Changing Velocity

Lesson 5 of 10 · 7 min · Free, no account needed

What you will learn

Acceleration is how much the velocity changes each second: change in velocity ÷ time.
Its unit is m/s²: metres per second, every second. 3 m/s² means 3 m/s faster each second.
Slowing down is acceleration too, against the motion. Steady acceleration adds the same amount every second, so the dots spread wider and wider.

An electric car does 0 to 100 km/h in 3 s. Where is its needle 1 s after the start?
A city bus needs 15 s for the same. Drag the needle to your guess for the car.
You hold the pedal. Set it, press Play, watch the dots.
The car starts from rest. A dot drops every second, and each bar is its speed at that second.
Four trails, one dot every second. Who left which?
Put each one on its trail.
The step in speed each second has a name.
Acceleration = change in velocity ÷ time. Here the car gains 3 m/s every second.
Unit: m/s², metres per second, every second. 3 m/s² means 3 m/s faster each second.
Braking is acceleration against the motion: -4 m/s² takes 4 m/s off every second. Simplified model: we keep the acceleration steady.
Plan a stop: a car at 12 m/s must stop exactly at the line, 18 m ahead.
Drag the bars: how fast is it at each second while it brakes? Then Check, and it drives your plan.
Game: stop at the line. Three red lights.
Press Drive, then Brake at the right moment. Stop within 1.5 m of the line, at three different speeds.
From math class: which table speeds up by the same amount every second?
Tap the row. In math, a steady step is a straight line with a slope.
0 to 100 km/h in 3 s. 100 km/h is about 27.8 m/s. What is the acceleration in m/s²?
Change in velocity ÷ time. One decimal place is enough.
Your best stop, one dot every second.
Press Play. Watch the gaps shrink once you brake.

Lessons are interactive and need JavaScript. Turn it on to play them.