What is force ? Write its SI UNIT?

Force is the push or pull on an object with mass that causes it to change its velocity.

Force is an external agent capable of changing the state of rest or motion of a body with mass.

Force is a vector quantity. It has a magnitude as well as direction.

The SI unit of Force is called Newton.

1 Newton = 1 Kg m/s²

A force of 1 newton is a force that is capable of accelerating a body of mass 1 Kg through an acceleration of 1 m/s^2.