# Trickey projectile motion question

1. Aug 4, 2008

### kilianod

trickey projectile motion question!!

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

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))}

2. Relevant equations
also given in the question is a general projectile equation

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

3. The attempt at a solution

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

2. Aug 5, 2008

### Kurdt

Staff Emeritus
Re: trickey projectile motion question!!

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.