## What is Mass?

A top spinning on the table, or a gyroscope spinning in space, tends to maintain its orientation. Any disturbance to this orientation is resisted. This is inertia. The resistance is coming purely from its spinning motion. Non-cyclic motion has no such inertia.

Inertia is the characteristics of a spinning or cyclic motion.

When we try to push a heavy metal ball hanging from a thread, it requires some force to move it. Most of the resistance is coming from its mass. This is also inertia. But this ball is not spinning. Its inertia is actually coming from the spinning particles within it.

The heavy metal ball is made of atoms. Each atom is like a whirlpool. Most of the inertia of the atom is coming from the spinning neutrons and protons in its nucleus. Spinning electrons may contribute to this inertia but that is negligible.

Mass of an object is the sum total of the inertia of all spinning nucleons within it.

Mass of an object has 2 different components

1. Inertia of one nucleon (proton or neutron).
2. The number of nucleons making up the object.

.