Mass and Momentum - 88tuition

Mass and Momentum - 88tuition

Pure Physics


The mass of a body refers to the total amount of matter present within it. All matter is made up of atoms and molecules. Thus, when we say that an object has a mass of "n kg", what we mean is that the sum of the masses of its atoms and molecules is "n kg". Further, we are aware that the motion of a body can be described in terms of its velocity and acceleration. However, velocity alone isn’t sufficient to determine the effect of motion and instead, we use a quantity known as the momentum for the same. In this article, we will try to understand what mass and momentum mean.

What is Mass?

The total amount of matter present within a body is known as its mass and mathematically, we can calculate it as

m denotes the mass of the body.

ρ denotes the density of the body.

V denotes the volume of the body.

From experience, you would know that trying to push an empty box is far easier than trying to push a box filled with heavy objects like bricks. Scientifically, this is related to the concept of mass, and objects with a larger mass require more force for moving. Thus, we can say that the mass of an object also measures its ability to resist a change in its state of motion. This property is known as inertia and has enormous applications in physics. 

You should remember that mass is a scalar quantity and thus, does not depend on direction. In SI units, it is measured in kilograms (kg)

What is Weight?

The weight of an object is related to the amount of force it exerts on the ground due to Earth’s gravitational pull. Since the gravitational pull of all planets is different, the weight of objects also differs from planet to planet. Mathematically, the weight of an object on Earth is:


Here m denotes the mass of the body and g denotes the acceleration due to the gravity of Earth, equal to 9.8 m/s². The concept of weight is different from that of mass, though the former depends on the latter. Here are a few important distinctions between the two.





Mass measures the amount of matter present in a body.

Weight measures the force exerted by an object due to gravity.


Mass remains constant weight

Weight can change from place to place, depending on gravitational pull.

Type of quantity mass

Mass is a scalar.

Weight is a vector.

SI Unit

Kilograms (kg)

Newtons (N)