Moderate Time, Speed & Distance Solved QuestionAptitude Discussion

 Q. A ball is projected vertically up-wards reaches, at the end of '$t$' seconds, an elevation of '$s$' feet where $s=160t−16t^2$. The highest elevation is
 ✖ A. 800 ✖ B. 640 ✔ C. 400 ✖ D. 320

Solution:
Option(C) is correct

Given that:

$s=160t−16t^2.$

Highest value of $S$ will be reached when $\dfrac{dS}{dt}=0$

$⇒ 160−32t=0$

$⇒ t=5$ sec

Thus $S=(160\times5)−(16\times 5\times 5)$

$=800−400$= 400