Explain Newton's second law of motion with suitable example?

Newton's second law of motion:
                    According to this law, 
                                                  “the force  acting 
on a body is directly proportional to the rate 
of change of linear momentum of the body 
and the change in momentum takes place in 
the direction of the force”.
This law helps us to measure the amount 
of force. So, it is also called as ‘law of force’. 

Let, ‘m’ be the mass of a moving body, moving 
along a straight line with an initial speed ‘u’ 
After a time interval of ‘t’, the velocity of the 
body changes to ‘v’ due to the impact of an 
unbalanced external force F.
Initial momentum of the body Pi = mu
Final momentum of the body Pf = mv 
Change in momentum
         Δp =Pf–Pi 
               = mv – mu
By Newton’s second law of motion, 
Force, F ∝ rate of change of momentum
F ∝ change in momentum / time
F ∝
mv – mu/t
F = km(v – u) /t
Here, k is the proportionality constant.
k = 1 in all systems of units. Hence,
F = m(v – u) t
Since, acceleration = change in velocity/
time, a=(v-u)/t.
 Hence, we have

F = m × a 

Force = mass × acceleration

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