f.4 phys,, about a ball

C 3x

In the first second:
s = ut + ( 1 / 2 ) * a * t^2 ------------------------- (1)
because "A ball is released from rest at time t=0 ", so, u = 0
(1) becomes: s = ( 1 / 2 ) * a * t^2 --------------- (2)
given that displacement of the ball in the first second = x,
it means s = x = ( 1 / 2 ) * a * t^2 ---------------- (3)

In the second second:
using (1) again,
but now, u is not equal to zero, u = at
from (3), x = ( 1 / 2 ) * a * t^2
so, a * t^2 = 2x,
so, ut = at * t = a*t^2 = 2x ---------------------- (4)
substitude (4) and (3) into (1),
we have, s = 2x + x = 3x

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C. 3x

In the first second,
u = 0
a = 10
t = 1

s = ut 1/2 at^2
s = 1/2 x 10 x 1
s = 5

In the 2nd second,
u = 0
a = 10
t = 2

s = ut 1/2 at^2
s = 1/2 x 10 x 4
s = 20

The distance travelled during 1s to 2s
20-5
= 15

If the distance travelled in 1s is x
the distance travelled during 1s to 2s is 3x

C. 3x

In the first second,
u = 0
a = 10
t = 1

s = ut 1/2 at^2
s = 1/2 x 10 x 1
s = 5

In the 2nd second,
u = 0
a = 10
t = 2

s = ut 1/2 at^2
s = 1/2 x 10 x 4
s = 20

The distance travelled during 1s to 2s
20-5
= 15

If the distance travelled in 1s is x
the distance travelled during 1s to 2s is 3x