A student states: 'Speed and velocity are the same thing.' Explain why this statement is incorrect, and describe the difference between a scalar quantity and a vector quantity, giving one example of each.

Speed and velocity are not the same because speed is a scalar quantity while velocity is a vector quantity.

Speed is the magnitude of motion only – it tells how fast an object is moving but gives no information about the direction of that motion. Velocity, on the other hand, is defined as the rate of change of displacement and therefore includes both a magnitude and a direction.

A scalar quantity has only magnitude; it can be expressed with a single number and a unit, for example temperature (30 °C). A vector quantity has both magnitude and direction; for example velocity (5 m s⁻¹ east).

Thus, speed is a scalar, velocity is a vector, and the examples of a scalar (temperature) and a vector (velocity) illustrate the difference.