Answer to Question #260490 in Physics for denkies

Question

A projectile is to be launched at an angle of 30 degrees so that it falls beyond a point of length 20m.

what is the range of value of the initial velocity so that the projectile falls between the points m and n

Answer 1

The velocity is

$$v=\sqrt{Rg/\sin(2 \theta)}=15\text{ m/s}.$$