Question

A stone thrown upwards, has its equation of motion $s=490t-4.9t^2.$ Then the maximum height reached by it, is

• A. 24500
• B. 12500
• C. 12250
• D. 25400

Answer 1

Answer: (C)

Given that
$s=490t-4.9t^2$
On differentiating w.r.t. $t$, we get
$\frac{ds}{dt}=490-9.8t$
A stone is reached the maximum height,
when $\frac{ds}{dt}=0$
$\Rightarrow 490-9.8t=0$
$\Rightarrow t=\frac{490}{9.8}$
$=\frac{100}{2}=50$
$\therefore$ Maximum height at $t=50$
$s=490(50)-4.9(50{)}^2$
$=24500-12250$
$=12250$