Question

Which is not the non-SI unit of force?
A) Dyne
B) Kg-force
C) Gram-force
D) $Kgm/{s^2}$

Answer 1

Hint: The push or pull of an object is called Force. Force is the product of the mass of the body ($M$) and acceleration ($a$). The main property of force is that it can stop a moving object or stationary object. The speed and direction can also be changed by the force. The equation of force is \[F = M \times a\].

Complete step by step answer:
SI unit of force is Newton($N$).
$N=Kgm/{s^2}$
Now we consider the given options and find which is not the non-SI unit of force:
A) Dyne is the CGS unit of force. So it is a non-SI unit of force.
B) Kg-force is a Gravitational Metric unit of force. So it is a non-SI unit of force.
C) Gram- force is a Gravitational Metric unit of force. So it is a non-SI unit of force.
D) $Kgm/{s^2}$ is the SI unit of force. So it is not the non-SI unit of force.

$\therefore $ We can say that option (D) is correct.

Note:
We get the definition of force from the 1st law of motion of Newton and then get the equation, units, and measurement of force from the 2nd law of motion.
There are four types of force named Gravity, Weak, Electromagnetic, and Strong.
There are four types of unit system of force:
(i) Cgs unit= $gm\, m/{s^2}$or Dyne.
(ii) SI unit= $Kgm/{s^2}$ or Newton.
(iii) FPS unit= \[lb{\text{ }}\dfrac{{ft}}{{{s^2}}}\] or Poundal.
(iv) Gravitational metric unit= kg-force, gram-force.