Velocity time graph

Equations and graphs Velocity time graph

Here is the graph that we created in the last lesson

If a line in a velocity-time graph is moving away from zero velocity then it shows increasing speed. A line moving towards zero shows decreasing speed. Zero gradient shows constant speed.

The gradient shows the acceleration. This is because accelaration is calculated as change in velocity divided by time taken.

$acceleration = \frac{change\ in\ velocity}{time\ taken}$

In the first thirty seconds the gradient is

$\frac{10m/s}{30s}$

$=\frac{1}{3}ms^{-2}$

This is read as acceleration of one third of a metre per second per second or one third of a metre per second squared. This means that the speed of the car is increasing by one third of a meter per second every second.

The gradient is 0 from 30 seconds to 330 seconds. This means no acceleration or deceleration. It means a constant speed.

From 330 seconds to 360 minutes the car slows down. We know this because the line is moving towards zero. The gradient is

$\frac{-10m/s}{30s}$

$=-\frac{1}{3}ms^{-2}$

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