Question

The rate of change of velocity is called speed. True or false
A) True
B) False

Answer 1

Hint: The unit to measure the total displacement traveled at a certain time is called velocity. It has both magnitude and direction. Hence the velocity can be either negative or positive. The sign of velocity changes according to the direction it takes. The average is the change of displacement per time ratio. The average velocity changes concerning time.

Complete step by step answer:
(i) Velocity is the rate of displacement traveled. The average velocity is the displacement traveled in a unit time. It has both magnitude and direction. Hence it is called a vector quantity.
(ii) Speed is the rate of distance traveled or the distance traveled in a unit time. Even though the velocity and speed sound the same, speed has only magnitude. Speed doesn’t say about the direction of the moving particle. Hence it is called a scalar quantity.
(iii) And the speed is not a rate of change of velocity because the rate of change of velocity is called acceleration.

The rate of change of velocity is not speed. The given statement is False. So, the correct option is B.

Additional information:
(i) In our normal day to day life, we don’t say velocity instead we use the term ‘speed’. The only difference between the velocity and speed is that velocity speaks about the direction of motion but the speed doesn’t.
(ii) Velocity is defined as the rate of displacement traveled.
(iii) Acceleration has both magnitude and direction. Hence it is a vector quantity.
(iv) According to Newton’s second law, acceleration is directly proportional to the force acting on the mass i.e. $F=ma$
(v) The SI unit of velocity is $m{s}^{-1}$. And the dimension of velocity is $L{T}^{-1}$.
(vi) Acceleration is the ratio of velocity and time. Hence its unit is $m{s}^{-2}$ and the dimension of acceleration is $L{T}^{-2}$.

Note:
The difference between the speed and velocity is that velocity is a vector quantity whereas the speed is a scalar quantity. The value of speed can be greater than the velocity as it doesn’t include the direction the particle takes. Hence, we can also say that displacement can never be greater than the distance.