The correct option is A 450 m
For the first 10 s:
Initial velocity, u = 0 (As the object starts from rest)
Final velocity, v = 30 m/s
Time, t = 10 s
Using first equation of motion, v = u + at
Acceleration, a=v−ut=30−010
⇒a=3m/s2
For the next 10 s:
Initial velocity, u = 30 m/s
Time, t = 10 s
Acceleration, a=3m/s2
Using second equation of motion, s=ut+12at2
⇒s=30×10+12×3×(10)2
⇒s=300+150
⇒s=450m
Hence, the correct answer is option (a).