# A Projectile motion problem, I need help.

## Homework Statement

A cannon fires successively two shells with velocity u=250 m/s;the first at angle $$\theta1$$=$$\pi/3$$ & the second shell at an angle $$\theta2$$=$$\pi/4$$ to the horizontal, the azimuth being same. Neglecting air drag, find the time interval between firings leading to colling of shells.

## Homework Equations

range R=(u^2sin2$$\theta$$)/g
Time of flight t=(2usin$$\theta$$)/g

## The Attempt at a Solution

I'm really confused &unable to figure out.
Book says that its 11s.