How can I calculate the Newton's second law?

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Answer 1 · 2018-04-09T07:07:26

Newton's second law states that external force #F# is directly proportional to the rate of change of momentum.

If initial velocity of an an object of mass #m# is #u# and after applying uniform force for #t# seconds, its reaches a final velocity becomes #v#,

then its initial momentum is #mxxu=m u# and final momentum is #mxxv=mv# and hence change in momentum is

#mv-m u=m(v-u)#

and as it has taken #t# seconds, rate of change of momentum is #(m(v-u))/t#

But in case of uniform accelaration #a#, we have #v=u+at#

or #(v-u)/t=a# and then rate of change in momentum is #ma#,

hence #Fpropma#

Now we can choose or define a unit of force that corrsponds to unit mass and unit accelaration and then we will have

#F=ma#