Question 5
Why is speed a scalar quantity?
The right answer is the one marked above.
Because it is worked out from distance, and distance has no direction. When distance is measured, the direction travelled is not taken into account. So the speed obtained from it has a magnitude but no direction.
Speed certainly has a magnitude — 50 km h-1 is a magnitude. It is only the direction that is missing, and that is what makes it a scalar. Velocity, worked out from displacement, is a vector, because displacement does carry a direction.