What is Newton’s first law of force?

Newton’s first law of force is: If no external force acts, a stationary object will remain at rest, and a moving object will continue to move in a straight path with uniform velocity.

That is, if no force is applied from outside, there will be no change in the kinetic state of the object. Here it is called external force because the force must be applied from outside. Not from within the object. That is, if you sit inside a bus and apply force on the bus itself, it will not. Rather, the bus should be pushed from outside.

In practical terms, Newton’s first law gives an idea of the nature of force. That is, force must be applied to change the motion of an object. So we can define the ball from here.

Also, this formula gives the idea of inertia. If no force acts, the object will remain as it is, from this idea we can also define inertia.