Question

What is the difference between Mass and Weight?

Why do we use mass instead of weight?

Answer 1

In scientific contexts, mass is the amount of "matter" in an object (though "matter" may be difficult to define), whereas weight is the force exerted on an object by gravity.

Answer 2

Mass is a measure of how much force it will take to change that path. ... Weight, on the other hand, is a measure of the amount of downwards force that gravity exerts on an object. This force increases with the object's mass: the more inertia it has, the harder gravity pulls.