Question

@Deepakrathee

Answer 1

use\[v ^{2}=u ^{2}+2fs\]
here u=0
so \[f=\frac{ v ^{2} }{ 2s }\]

Answer 2

v^2 - u^2 = 2as

v is 30 m/sec
u is zero
s is 49 m
you will get the value of acceleration a

then use equation
v = u + at

v is 30m/sec
u is zero
a you have find from above
now you will get the time t, which will be 3.26 sec