How is force calculated?

We learn equation  F=ma but by seeing this equation can you visualise anything? Means how this works?

 Force means rate of change of momentum given by Sir issac newton. What is meant by rate of change of momentum? What means 1 newton force actually?

Suppose a sphere A is moving in space. Sphere A have mass 1kg . Sphere A is moving with 1km/sec.

Force exerted on Sphere A= mass of sphere A x its velocity change.

Now suppose we give push to sphere A causing its velocity changes to 2km/sec. 

Now change in momentum = how much is mass of moving object x how much velocity changes while force is applied.

It means force depends upon mass of object & its velocity change.

Now if we change sphere A mass to 2kg. What happens if same push is provided?

Its velocity will not increase to 2km/sec. Beacase same force tries to move more mass causing that force gets divided into more tiny matter of sphere A and resultant force on  each particle of sphere gets reduced. Hence sphere A of 2kg moves but with less velocity. Means same force can move different masses to different velocities. More the mass, less velocity change & less mass ,more velocity change.

Hence what force means , how much mass x how much velocity change . For given mass ,change in its velocity after force is applied gives exact value of force applied.