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Speed, velocity and acceleration

Speed

Speed is a scalar quantity and is the rate of which an object covers a distance

Speed can be calculated using the equation:

Speed = distance/time

  • Speed - measured in meters per second (m/s)

  • Distance - measured in meters (m)

  • Time - measured in seconds (s)

Worked example:

A car travels 100 m in 10 s. Work out its average speed.

  • Speed = distance/time

  • Speed = 100/10

  • Speed = 10 m/s

Velocity 

Unlike speed, velocity is a vector quantity, meaning it has a magnitude and direction.

Velocity is calculated by the change in distance divided by the time taken.

Velocity = d/t

  • Velocity - measured in meters per second (m/s)

  • distance moved  measured in meters (m)

  • time taken - measured in seconds (s)

A (-) velocity means that the object is moving backwards and a (+) velocity means that it is moving forward. 

Acceleration 

Acceleration can be calculated  by using the equation:

A=(V-U)/T

Acceleration = change in velocity/time taken 

  • Acceleration (A) - measured in meters per second (m/s)

  • Change in velocity (V-U) - measured in (m/s)

  • Time taken (T) - measured in seconds (s)

For example, a lorry accelerates in 5 s from 25 m/s to 35 m/s. Its velocity changes by 35 - 25 = 10 m/s. This means the lorry's acceleration is 10 ÷ 5 = 2 m/s2