Question

Assertion: Kilogram is a standard unit of mass.
Reason: Kilogram is well defined and invariant.

Answer 1

Hint: In physics, Inertia is a tendency to do nothing or to remain unchanged. Mass, in physics, a quantitative measure of this inertia, a fundamental property of all matter. It acts as a resistance that a body offers to a change in its speed or position when a force is applied on the body.

Complete answer:
We need to know that, Mass is both a property of the physical body and a measure of its resistance to acceleration (which is rate of change of velocity with respect to time) when a net force is applied.An object’s mass also determines the strength of its gravitational attraction to other bodies.Mass is denoted by m and its SI units is Kilogram which is represented by $Kg$. Hence, Assertion: Kilogram is a standard unit of mass is correct.

Kilogram was originally defined as- A kilogram is very nearly equal to the mass of $1000$ cubic cm of water. In gram conversion kilogram is related as $1\,kg = 1000\,gm$. Hence Kilogram is well defined and its invariant which shows us that given Reason: Kilogram is well defined and invariant is also correct and it’s the right explanation for given assertion.

So, both assertion and reason are correct and reason is the correct explanation for assertion.

Note:Currently, the Kilogram has a very simple definition: It’s the mass of a hunk of platinum-iridium alloy that’s been housed at the International Bureau of Weights and Measures in France since 1889. It’s called the International Prototype Kilogram.