Question

The units of speed and velocity are the same in the S.I. system. True or false.
A. True
B. False

Answer 1

Recall the difference between velocity and speed. We know that instantaneous velocity of the body is commonly known as speed of the body. The S.I. the unit of velocity is m/s.

Complete step by step answer:
To answer this question we have to explain the difference between velocity and speed.
The velocity of a body is the distance travelled by the body per unit time. If we want to calculate the velocity of the body, we take the ratio of distance travelled by the body and the time required to cover this distance. We know that velocity has both direction and magnitude.
Since the velocity is displacement divided by time, we can write,
${\text{velocity}} = \dfrac{{{\text{Distance}}}}{{{\text{Time}}}}$
We know that S.I. The unit of displacement is meter while S.I. unit of time is second. Therefore,
$v\left( {{\text{unit}}\,{\text{S}}{\text{.I}}{\text{.}}} \right) = \dfrac{m}{s}$
Now, the speed is the magnitude of velocity. When we say speed of the body, it is the instantaneous velocity of the body at that instant of time. It has no direction. Therefore, the S.I. unit of the speed must be m/s.
Therefore, the statement is true.

So, the correct answer is option (A).

Additional information: The S.I. units of other physicals variables are,
Acceleration: it is the ratio of change in velocity of the body to the elapsed time. Therefore, the S.I. the unit of acceleration is $m/{s^2}$.
Linear momentum: It is the product of mass of the body and velocity. Therefore, the S.I. unit of momentum is $kg \cdot \,m/s$.

Note:
The terms velocity and speed are incorrectly used to express how fast the body is moving. If the velocity of the body does not change with time, then we can say that it is the speed. We don’t use the term velocity of light to express how fast the light moves. Rather we use the speed of light because it is constant at any instant of time.