v = u + at
Given,
Retardation = -a = -25 cm s-2
Hence, -a = -0.25 m s-2
t = 20 s
v = 0
u = ?
Substituting the values in the formula above we get,
0 = u + (-0.25) × 20
or, 0 = u – 5
or, u = 5 ms-1
Hence, the initial velocity of bus = 5 m s-1
(ii) As we know, from the equation of motion,
v2 = u2 + 2aS
Substituting the values, we get,
02 = 52 + 2 × (-0.25) × S
or, 0 = 25 – 0.50 × S
or, 0.50 × S = 25
or, S = 25/0.5 = 50 m
Hence, distance travelled = 50 m