The correct option is B 53 m/s,21 m/s
Given, speed of the particle as v(t)=3t2+5
So, the speed of the particle at t=4 sec, is given as
v(t=4 sec)=3×42+5=53 m/s
Now, average speed of the car is given by
Total distance covered (S)Total time taken (t)
Given, the speed of the car is v(t)=3t2+5
and, distance =∫t0v(t)dt
⇒ S=∫40(3t2+5)dt=[t3+5t]40
⇒ S=(43+5×4)−(0+0)=84 m
Thus, average speed of the car is 844=21 m/s