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Motion In Straight Line

Question
CBSEENPH11026356

The displacement x of a particle varies with time t as x = ae-αt + beβt where a, b, α and β are positive constants. The velocity of the particle will

  • decrease with time

  • be independent of α and β

  • drop to zero when α = β

  • increase with time

Solution

D.

increase with time

Given:- 

        x = a e-αt + beβt

We know that

   velocity v = dxdt

              v  =  d dt ae-αt + beβt 

                  = -aα e-αt + bβ eβt

              v = -a αe-αt +  eβt

               v = A + B

where A = - aα e-αt , B = bβ e-βt

The value ot term A = -aα e-αt increases and of term B = bβ e-βt increases with time. As a result velocity goes on increasing with time.