Question

A particle is projected at an angle of ${45}^0$ from $8m$ before the foot of a wall, just touches the top of the wall and falls on the ground on the opposite side at a distance $4m$ from it. The height of wall is:

• A. $\frac{2}{3}m$
• B. $\frac{4}{3}m$
• C. $\frac{8}{3}m$
• D. $\frac{3}{4}m$

Answer 1

Answer: (C)

$\frac{8}{3}m$

At ${45}^o$ range of projectile $8+4=R=\frac{u^2}{g}{u}^2=12g$

Height of wall$=y=xtan\theta -\frac{g{x}^2}{2u^{2}co{s}^2\theta }=8\ast tan\left(45\right)-\frac{g\ast 8\ast 8}{2\ast 12g\ast (1/\sqrt{2{)}^2}}=8-\frac{8\ast 2}{3}=\frac{8}{3}m$