Question

A quantity is measured to be$-30m/s$. Is it speed or velocity? Give a reason for your answer.

Answer 1

The quantity is measured to be $-30m/s$.

1. The basic difference between Speed and Velocity is that speed is a scalar quantity whereas velocity is a vector quantity.
2. In simpler words, velocity is a speed with direction and on the other hand, the speed has no element of the direction of motion involved in its expression.
3. Therefore, if the quantity is measured or expressed as '-30 m/s', then the negative symbol is an indicator of a motion which is opposite to the direction of the force applied.
4. With the element of direction in its expression, it can be concluded that the above quantity is an expression velocity and not the speed.

Hence, the quantity is velocity.