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Acceleration and velocity-time graphs
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Acceleration is how quickly velocity changes. Graphs make it easy to see and to calculate.
The equation
acceleration = change in velocity ÷ time taken
a = (v − u) ÷ t
u is the starting velocity and v is the final velocity. The unit is m/s2.
A negative acceleration means slowing down (deceleration).
a = (v − u) ÷ t
u is the starting velocity and v is the final velocity. The unit is m/s2.
A negative acceleration means slowing down (deceleration).
Velocity-time graphs
The gradient is the acceleration.
The area under the line is the distance travelled.
A flat line means constant velocity.
The area under the line is the distance travelled.
A flat line means constant velocity.
The other motion equation
v2 − u2 = 2 × a × x
x is the distance. Use it when time is not given.
x is the distance. Use it when time is not given.
A car speeds up from 0 to 24 m/s in 8 s. Find its acceleration.
- a = (v − u) ÷ t
- a = (24 − 0) ÷ 8
- = 3 m/s2
Answer: 3 m/s2
a = (v − u) ÷ t in m/s2. On a velocity-time graph, gradient is acceleration and area is distance. Use v2 − u2 = 2ax when there is no time.
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