Question

The S.I unit of momentum is:
A. $kgm{s}^{-1}$
B. $kgm{s}^{-2}$
C. $kgm{s}^2$
D. $kg{m}^{-1}{s}^{-1}$.

Answer 1

- Hint: Let us write the formula of heat because after expanding that we can easily calculate the unit of momentum.

Complete step-by-step solution -

We know that Momentum can be defined as the product of the mass of a particle and its velocity. Momentum is a vector quantity; i.e., it has both magnitude and direction.
Momentum is denoted by P.
We know that, the formula of momentum, P = mV
Where, m is the mass of the body and we know that mass is a scalar quantity and it’s unit is kilogram ( kg ) .
V is the velocity of the body and velocity is a vector quantity whose formula is ,
$\Rightarrow V={\displaystyle \frac{displacement}{time}}$ , now the unit of velocity can be obtained by,
 Unit of V = ${\displaystyle \frac{unitofdisplacement}{unitoftime}}$
 Unit of V = ${\displaystyle \frac{metre(m)}{\sec ond(s)}}$
 Unit of V =${\displaystyle \frac{metre}{second}}$ = $m{s}^{-1}$
Now, momentum, P = mV
Unit of momentum = unit of mass $\times$ unit of velocity
Unit of P = kg $\times m{s}^{-1}$
Unit of P = kgm$s^{-1}$
So the SI unit of momentum is $kgm{s}^{-1}$.
Therefore, the correct answer is option(A).

Note: Whenever we come up with this type of problem where we are asked to find the unit of any quantity. Then we first write the formula to calculate that quantity and then in place of the quantities involved in the formula we will put the unit of every quantity. After simplifying that we will get the required S.I. unit asked for that quantity (here momentum).