Question

Although we know that a moving body keeps moving indefinitely until an external force is applied on it then why does a ball stops when we slide it on ground (without stopping it)

Answer 1

We know that a moving body keeps moving indefinitely till no external force is applied to stop it's motion.

But

When a ball slides on ground,it finally comes to rest.

why?

well , here's your answer

This is because of force of friction.
not familiar with it?
let me explain

This is a force that can stop moving things or can prevent stationary objects from moving.
It is a contact force, meaning, is caused due to contact between two surfaces

Friction is actually caused due to interlocking of irregularities present in the two surfaces.
These aren't generally visible with a naked eye.
when we go to microscopic level, we will find them and these are present in all objects.


So when the ball is rolled on ground,
the irregularities,in the form of grooves and ridges get interlocked thereby opposing motion.


hope helped.

here's an attachment for better understanding

Answer 2

because of many factors like
friction
gravitation
etc.
these are external forces which stops the ball