A body travels a distance s in t seconds.  It starts from rest and ends at rest.  In the first part of the journey, it moves with constant acceleration f and in the second part with constant retardation r.  The value of t is given by

 

a)  2s divided by 1/f + 1/r

 

b) square root of 2s(f+r)

 

c) square root of 2s(1/f + 1/r)

 

d) 2s(1/f + 1/r)