Question

A quantity is measured to be $-20\mathrm{m}/\mathrm{s}$. Is it speed or velocity? Give reasons.

Answer 1

1. Speed is defined as the distance travelled per unit of time.
2. $\mathrm{Speed}=\frac{\mathrm{Distance}}{\mathrm{Time}}$.
3. As distance and time are positive quantities, so does speed.
4. Velocity is defined as the distance traveled per unit of time in a particular direction.
5. Velocity has a particular direction making it a vector.
6. So, velocity can be positive or negative.
7. The SI unit of velocity and speed are the same i.e. $\mathrm{m}/\mathrm{s}.$
8. Therefore, the given quantity will be velocity as speed can't be negative.