Question

The maximum height of a projectile for two complementary angles of projection is 50 m and 30 m respectively. The initial speed of projectile is

• A. $10\sqrt{34}$ m/s
• B. 40 m/s
• C. 20 m/s
• D. 10 m/s

Answer 1

The correct option is B 40 m/s

For angle of projection $\theta ,$ $H_1=\frac{u^{2}si{n}^2\theta }{2g}$
For angle of projection ${90}^{\circ }-\theta$,
$H_2=\frac{u^{2}co{s}^2\theta }{2g}$
$H_1+H_2=\frac{u^2}{2g}$
$u=\sqrt{2g(H_1+H_2)}=40m/s$
$\therefore \left(b\right)$