Question

The equation of trajectory of a projectile is $y=10x-\left[\frac{5}{9}\right]x^2,\left(m\right)$. The maximum height is reached when $x$ is

• A. $36m$
• B. $24m$
• C. $18m$
• D. $9m$

Answer 1

Answer: (D)

$9m$

For maximum height:
$\frac{dy}{dx}=0\Rightarrow \frac{d}{dx}(10x-\frac{5}{9}{x}^2)=0$

$\Rightarrow 10-\frac{10}{9}x=0$

$\Rightarrow x=9m$