Trickey projectile motion question

[kilianod]

trickey projectile motion question!

Homework Statement

1. (i)A shell is fired with speed 'U' from a point on a cliff of height 'h' above sea level. Show that the greatest horizontal distance that the shell can travel before reaching the sea is

(U/g)(U^2 + 2gh)^(1/2)

(ii)and that the angle for maximum distance is

tan^(-1){U/((U^2 + 2gh)^(1/2))}

Homework Equations

also given in the question is a general projectile equation

y= (x)(tan(a) - {(g)(x^2)}/{(2)(U^2)((cos(a))^2)}

The Attempt at a Solution

Ive repeatedly attempted this with little success, i think the key is use of trigonometric substitutions, but I am not sure. Please Help!

 

[Kurdt]

Well for the first part I assume the projectile is fired horizontally. The maximum distance it can travel depends on its travel time. The travel time all depends on the height of the cliff. With these questions you need to consider horizontal and vertical components separately.