The correct option is A 15ms−1
S=100m,vavg=20m/s,v=25m/s
Time taken to cover the distance, t=Svavg=10020=5s
From, v=u+at
25=u+a∗5
a=25−u5
Putting the value of a in v2=u2+2aS
252=u2+2∗25−u5∗100
u2−40u+375=0
On solving, we get two values of u as 15m/s and 25m/s.
Since, final velocity is 25 m/s, initial velocity is 15 m/s.