Solution :
In question it is given that,
Initial speed, u = 20 km/h
= 20 × 1000m / 60 ×60s
= 5.55 m/s
Final speed, v = 60km/h
= 60 × 1000m/60 ×60 s
= 16.66 m/s
Acceleration, a =? ( To be calculated)
time, t = 6s
v = u+ at
16.66 = 5.55 + a × 6
6 a = 16.66 - 5.55
6 a = 11.11
a = 11.11/6
a = 1.85 m/s2
Thus the acceleration is 1.85 m/s2.