Question

To obtain a given range of a projectile, there are two possible angles of projection with the horizontal. If $R$ is the range for an angle of projection of ${25}^o$, then the other possible angle of projection is

• A. ${20}^o$
• B. ${65}^o$
• C. ${70}^o$
• D. ${90}^o$

Answer 1

The correct option is B ${65}^o$

The given range is same for two complementary angles ie rang is same for ${\theta }_1$ and ${\theta }_2$
if ${\theta }_1+{\theta }_2={90}^o$
Given, ${\theta }_1={25}^o$
$\therefore {25}^o+{\theta }_2={90}^o$
$\Rightarrow {\theta }_2={90}^o-{25}^o={65}^o$