Q. A stone is thrown vertically upwards from the top of a tower 64 m high according to the law s=48t-16$t^{2}.$The greatest height attained by the stone above ground is
A) 36 m
B) 32 m
C) 100 m
D) 64 m
Explanation
(c)
Given , $s = 48t - 16t^{2}$
$\Rightarrow \frac{ds}{dt} = 48 - 32t$
At the greatest height, v=$\frac{ds}{dt} = 0$
$\Rightarrow$ 48-32t=0
$\Rightarrow \ \ \ t = \frac{3}{2}$
$\therefore\ \ s = 48 \times \frac{3}{2} - 16\left( \frac{3}{2} \right)^{2} = 36m$
$\therefore\ \ \ Total\ height = 64 + 36 = 100m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.