Question

From a point on the ground at a distance $2m$ from the foot of a vertical wall, a ball is thrown at an angle of ${45}^{\circ }$ which just clear the top of the wall and afterwards strikes the ground at a distance $4m$ on the other side. The height of the wall is

• A. $\frac{2}{3}m$
• B. $\frac{3}{4}m$
• C. $\frac{1}{3}m$
• D. $\frac{4}{3}m$

Answer 1

Answer: (D)

$\frac{4}{3}m$

$R=\frac{u^2}{g}$ or $6=\frac{u^2}{g};$

$y=x\tan \theta -\frac{g{x}^2}{2u^2{\cos }^2\theta }$
$⟹h=2\tan {45}^{\circ }-\frac{4}{2{\cos }^2{45}^{\circ }}\left(\frac{1}{6}\right)=2-\frac{2}{3}=\frac{4}{3}m$