1. The problem statement, all variables and given/known data

A gun on the shore (at sea level) fires a shot at a ship which is heading directly toward the gun at a speed of 40 km/h. At the instant of firing, the distance to the ship is 15,000 m. The muzzle velocity of the shot is 700 m/s. Pretend that there is no air resistance.

(a) What is the required elevation angle for the gun? Assume g = 9.80 m/s^2.

(b) What is the time interval between firing and impact?

2. Relevant equations

Uhmm, I'm guessing. $\displaystyle t_{flight} = \frac{2v_{0} sin\alpha }{g} $

Maybe $\displaystyle x_{max} = \frac{v^{2}_{0}sin2\alpha}{g} $ will also be applicable.

$\displaystyle v_{x} = v_{0x} = v_{0}cos\alpha $

$\displaystyle v_{z} = v_{0z} - gt = v_{0} sin \alpha - gt $

$\displaystyle x = v_{0x}t $

$\displaystyle z = v_{0z}t - \frac{1}{2} gt^2 $

3. The attempt at a solution

I'm not sure what to do with this problem. Any way I set it up, I end up with more variables than I can solve for.

I would appreciate a hint to throw me in the right direction. Thanks in advance.