Projectile Motion: Cannons (1 Viewer)

[DRFTR]

Hi guys, we were given that when two objects were launched at each other, but at different heights, the two objects will collide with each other if the velocity of the objects is great enough.
Does anyone know how can we calculate the minimum velocity for this or is there a forumla for this?
Thnx ^^

 

[helper]

Same formulas as for one but solving simultaeously