Cannon... Σ(ﾟДﾟ；

Found a useful simulation for projectile motion~
http://phet.colorado.edu/sims/projectile-motion/projectile-motion_en.html

After a few trials, it is discovered that the launge angle of 45 degree enables the bullet to travel the maximum distance...

Then I found that, the larger the velocity the cannonball has, the longer the distance it can travel...

Some websites said that a longer barrel gives a higher velocity to the cannonball since the long length of the barrel gives a longer distance for the ball to gain acceleration. But for the cannon we are going to make, the cannonball is places at the exit of the cannon so I think this theory may not be useful here...