A horizontal line means the object is moving at a constant speed. The gradient of the line = the rate of change of speed. The steeper the line, the greater the increase in speed. The area under the ...

gradient = \(\frac{change~in~y}{change~in~x} = \frac{change~in~speed}{change~in~time} = \) \( \frac{change~in~metres~per~second}{change~in~seconds}\) = metres per ...