Acceleration is the rate of change of velocity, a = Δv/Δt — the slope of a velocity–time graph. Drag the sliders below to set the initial velocity and the acceleration, and watch the motion animate beside a live velocity–time graph.
The steepness of the line on a velocity–time graph is the acceleration — tilt and quantity are one and the same, so you can read acceleration straight off the gradient without any arithmetic. This simulator gives you just two sliders, Initial velocity u and Acceleration a, then animates the motion beside a live v–t graph. Because a stays constant, the trace is always a straight line: the value of u sets where it starts on the vertical axis, and a sets how sharply it climbs or falls as the velocity builds by v = u + a·t.
What acceleration really measures is the rate of change of velocity, a = Δv / Δt in m/s² — the slope of that line, never the height of it. Slide a steeper and the line tilts up faster; flatten it to zero and the line goes horizontal, meaning the velocity holds constant. That flat case is the classic trap: zero acceleration is not zero velocity. An object can cruise at a large steady speed with a perfectly level trace, while a big acceleration can strike at the very instant the velocity reads zero, as something leaves rest.
Push a negative and the line slopes downward, steadily lowering the velocity: that slows a forward-moving object to a stop and then reverses it — though the very same downward slope would speed up something already heading backwards, which is why a negative acceleration does not simply mean “slowing down”. To carry this slope into the full equations of motion, open the SUVAT lab, check your figures with the acceleration calculator, or browse the wider shelf of interactive physics labs.
Acceleration is the rate of change of velocity, a = Δv/Δt, measured in m/s². On a velocity-time graph it is the slope of the line.
No. Zero acceleration means constant velocity — a flat, horizontal line on a velocity-time graph. An object can move at a large steady speed with zero acceleration.
It is the slope (gradient) of the line, not its height. A steeper line means a bigger acceleration; a horizontal line means zero acceleration; a downward slope means a negative acceleration.
For an object moving forwards, a negative acceleration lowers its velocity — slowing it, and eventually reversing it. The same negative acceleration would speed up an object already moving backwards, so 'negative' does not simply mean 'slowing down'.