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. 

ball thrown upwards go staright and come down? Is that happens actually? or something else?

When ball is thrown upward towards sky it goes straight and come down . This is what we see.

But in reality something different happens.

When ball is thrown upward, it follows curved geometry as ball and us both are moving (earth rotates around itself) .

Ball's velocity has three vectors 1. Ball thrown towards sky 2.opposing gravity 3.earth's rotational velocity. Both 3 vectors act at same time.

Now ball's up force is more than gravity ,so ball moves upward but gravity constantly at every second opposes ball .this causes ball's velocity go on decreasing. But at same time ball is rotating with earth surface in perpendiculardirection to thrown force. Resultant ,ball follows curved path as shown. But we too moving with earth surface ,we can't experience its curved path we just see it goes straight upward and come downward.

Above curved path of ball is also relative means  someone outside earth can  sees this path.if same observer goes outside to solar system, path is  again different. Take look at below .

Earth rotates in circular path around sun generally perceived. 

But see below

sun also rotates around galaxy center so relative to observer outside solar system ,earth follows sinusoidal path around sun.

All the motions are relative to observer speed and location .

Why rolling motion requires less force than sliding motion to move same mass?

Have you ever wondered why rolling motion moves heavy weight from one place to another with less force? Science behind lies ,we will explore here:-

   See below image

 ,when object is round in shape(sphere) it contact with earth surface is only a single point (theoretically),practically a tiny space. Whole weight of sphere is resting on that single point.Now split sphere into two parts vertically,

 Now compare this split with seesaw.

Weight w1 & w2 are hanging like cantilever beam from split line. Now weight force downwards ( w1 & w2 ) are same in both side, balance is maintained ,thats why sphere is not moving . If we add 1gram of material to one side what will happen?

 This 1 gram creates unbalance of forces hanging on central split line.this causes to sphere starts tilting on 1gram side due to more weight.

This tilt creates rotating motion.

 Now compare  1gram  with push force by us on top side.

It will cause imbalance and sphere starts moving in straight line.once it gets rotating motion.it keeps rotating (theoretically) until opposite force is applied.in real sphere stops rotating beacause of friction on contact point by land.