How to solve problems of physics? (i)

In this part of the discussion we will be dealing in general about solving problems based on newton's second law. Newton's second law states that the force exerted on the body is directly proportional to the rate of change of momentum and this change takes place in the direction of the force.
Now, let us try to formulate the law in a more mathematical way.
F is proportional to rate of change of momentum
or F = K. mv(final) - mv(initial) /time
or F = K. m(v(final) -v(initial))/time
We know that acceleration of a body is defined as the rate of change of velocity
or a = v(final) -v(initial)/time
Therefore we have the mathematical form of newton's second law as
F = ma
Although the equation looks simple but let me tell you it is one of the most important equation that has ever been formulated. Almost every problem of mechanics can be solved using this equation.

Since, now you must have had a fair bit of understanding of what the law states. Lets begin with one example which will help you understand the approach to solve problems related to newton's second law.
Here are the meanings of the symbols used in the equations
F= force (S.I units N(newton)
a= acceleration (S.I unit m/s^2)
m= mass of the body (S.I unit Kg)
v(initial) = initial velocity of the body (S.I unit m/s)
v(final) = final velocity of the body (S.I unit m/s)
t= time (seconds)