Speed and Velocity

This lesson covers speed, velocity, and distance-time graphs — as required by the Edexcel GCSE Physics specification (1PH0), Topic 1: Key Concepts of Physics. You need to be able to calculate speed and velocity, recall typical speeds, and interpret distance-time graphs.

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Speed

Speed is a scalar quantity that measures how fast an object is moving. It is defined as the distance travelled per unit time.

speed = distance ÷ time

$s = \frac{d}{t}$s=td​

Where:

• s = speed (m/s)
• d = distance (m)
• t = time (s)

This can be rearranged:

• d = s × t (distance = speed × time)
• t = d ÷ s (time = distance ÷ speed)

Exam Tip: Remember the formula triangle — put d on top, s and t on the bottom. Cover the quantity you want to find: d = s × t, s = d/t, t = d/s.

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Velocity

Velocity is a vector quantity — it is the speed in a given direction, or more precisely, the rate of change of displacement.

velocity = displacement ÷ time

$v = \frac{x}{t}$v=tx​