Velocity-time graphs show how the velocity of a moving object changes with time.
The table shows what each section of the graph represents:
|Section of graph||Gradient||Velocity||Acceleration|
|D||Zero||Stationary (at rest, v = 0)||Zero|
The slope or gradient of a velocity-time graph =
The velocity-time graph above is for a racing car accelerating from rest.
What is the acceleration in the first 10 s?
Acceleration = the gradient of the graph =
= (40 m/s – 0 m/s) ÷ 10 s
= 40 m/s ÷ 10 s
= 4 m/s2
The acceleration of the car in the first 10 s is 4 m/s2.
What is the acceleration of the car between 30 s and 50 s?
Acceleration is the gradient of the graph =
= (0 m/s – 60 m/s) ÷ 20 s
= -60 m/s ÷ 20 s
= -3 m/s2
The car has an acceleration of -3 m/s2 (or a retardation of 3 m/s2).