Answer:
the required value is 
Explanation:
Given that,
mass, m = 1kg
spring constant k = 21N/M
damping force = 

By Newtons second law ,
The diffrential equation of motion with damping is given by

substitute the value of m =1kg, k = 21N/M, and 


suppose the equation of the form
,
and the auxilliary equation is given by

The general solution for the above differential equation is

Derivate with respect to t

(a)
since time is 0 then mass is one meter below
so x(0) = 1
Also it start from rest , that implies , velocity is 0 and time is 0

substitute the initial condition


Solve the above equation to get C₁ and C₂

substitute for C₁ and C₂ in general solution

Thus the required value is 