An object is going to be launched from the ground with an initial velocity of $v$. It starts a distance $d$ away from a wall of height $h$. Assume that the wall is close enough that any angle $\Theta < 45 \degree$ would not make it over the wall. Find $\Theta$ to maximize the horizontal distance the object travels, and it must pass over the wall?
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In projectile motion, the horizontal and vertical motion are independent. The horizontal motion is constant velocity and the vertical motion is constant acceleration (acceleration due to gravity).
Horizontal Motion
$v_x=\frac{d}{t} \tag{1}$
$t=\frac{d}{v_x} \tag{2}$
$t=\frac{d}{v \cdot cos \ \theta} \tag{3}$
Vertical Motion
$h=v_{0,y}t \ + \ \frac{1}{2} gt^2 \tag{4}$
Substitute horizontal time into equation 4
$h=v \cdot sin \ \theta \cdot \frac{d}{v \cdot cos \ \theta} \ + \ \frac{1}{2} g \Biggr(\frac{d}{v \cdot cos \ \theta} \Biggr) ^2 \tag{5}$
$h=d \cdot tan \ \theta \ - \ \frac{g d^2}{2v^2 cos^2 \ \theta} \tag{6}$