1. The problem statement, all variables and given/known data A 20.0 kg cannonball is fired from a cannon with a muzzle speed of 1050 m/s at an angle of 42.0° with the horizontal. A second ball is fired at an angle of 90.0°. (a) Use the isolated system model to find the maximum height reached by each ball. (b) What is the total mechanical energy of the ball-Earth system at the maximum height for each ball? Let y = 0 at the cannon. 2. Relevant equations Ei = Ef K = (1/2)mv^2 U = mgy 3. The attempt at a solution I know that you can solve for h by setting these two equal, but I don't understand why that works. I need to understand how these relate. I have no idea what to do for b. Thank You.