linear velocity is great for missiles and linear impulse is for turrets. When you apply linearVelocity your physical body starts to accelerate from zero to a speed defined by the damping. When you apply impulse your body will have the desired speed instantly in the beginning of the movement and will start decelerating at same moment too.
Comments
About angle, well it's the both vector's x and y that provides an angle.
Here is the blog post on slingshot, which will be pretty the same when launching a canon ball:
http://appcodingeasy.com/Gideros-Mobile/Gideros--Box2d-Slingshot
Likes: Tom2012
Thanks for that - I've solved the problem after looking at your tutorial again. Thank you!