We have to first ind the retardation.
Using the third equation of motion: v2 – u2 = 2
as
where: s = distance covered = 10 m
v = final velocity = 0 m/s (brakes are applied so that buscomes to rest)
u = initial velocity = 72 km/
h = 20 m/s
a = acceleration = ? m/s2
v2 – u2 = 2
as
0 – 202 = 2 × a × 10
-400 = 20 × a
- \(\frac{400}{20}\)= a
a = -20 m/s2
Now, u = initial velocity = 144 km/h = 40 m/s
s = distance covered = ?? m
v = final velocity = 0 m/s ( brakes are applied so that bus comes to rest)
a = acceleration = -20 m/s2
Using the third equation of motion: v2 – u2 = 2
as
0 – 402 = 2 × -20 × s
-1600 = -40 × s
-\(\frac{1600}{-40}\)= s
s = 40 m