Question

Explain newton's second law of motion in the simplest lanvuage possible

Answer 1

rate of change of momentom is directly proportional to the applied force

Answer 2

Newton's second is actually tells how we can measure a force...Force is a measurable quantity , This measurement can be done by using Newtons 2nd Law...
More simply i could say...Newtons 2nd law gives the measurement of force...

To understand 2nd law , One must have knowledge of a physical quantity called Momentum...

Without this quantity , You cannot understand this law...

Momentum is a effect of motion...This can be measured as the product of mass and velocity of a body...Moemntum is denoted by a letter p...so
Momentum , p = mass ( m ) × velocity ( v )...

Momentum is a conserve ( constant ) quantity untill there is an external force ...which mean if net force on a body is 0 , then momentum of a body is conserve...

Suppose a ball of mass m is coming towards you with some velocity 2 m/s, say....

lets observe the situation at time ,
t = 0 => here u ( initial velovity) = 2 m/s and mass = m kg Initial Momentum p1 = m × u = m × 2 = 2m

Now at some time t = 5 seconds , we observed that v ( final velocity ) = 2 m/s and m ( mass ) = m kg
Then Final momentum , p2 = m × v = m × 2 = 2m

Now Change in momentum
= Final momentum - Initial Momentum
= p2 - p1
= 2m - 2m = 0
Here you can see Final momentum and Initial momentum of a ball is same so we say momentum is conserved or constant....

But in order to change the momentum of a ball you need to apply a force on a ball...

So Force is resposible to change the momentum...

This is what we call 2nd law of motion..

Statement => Force applied on a body is directly proportional to the rate of change of momentum...

i.e , F directly proportion to rate of change in momentum
F depends on rate of change of momwntum
F depends on ( p2 - p1 ) / t
F = k ( p2 - p1 ) / t
F = k ( mv - mu ) / t = k m [ ( v - u ) / t ] = k × m × a
F = kma ---- ( i )

take k = 1 in ( i ) we get F = m × a

This is how we calculate force ...This measurement is derived using Newtons 2 d law of motion...