Question

A projectile is fired at an angle of 30o with the horizontal with velocity 10m/s. At what angle with the vertical should it be fired to get maximum range?

CLASS - XI PHYSICS (Kinematics)

Answer 1

Range = $\frac{ v^{2}sin(2 \alpha ) }{g}$

where α=angle with horizontal.
we get α=45° for maximum range. 
So angle with vertical = 90° - 45° = 45°

v = 10m/s
Range = 10²×sin(60)/9.8 = 8.8m
maximum range = 10²×sin(90)/9.8 = 10.2m

Answer 2

max range is v*v*sin*2a/g
so the answer is 10.2 m