Answer:
786 J
Explanation:
Let g = 9.81 m/s2. The vertical distance that the canon ball must have traveled within 1.65 s is (ignoring air resistance):
[tex]h = gt^2/2 = 9.81*1.65^2/2 = 13.35 m[/tex]
So the work done by gravity would be the product of gravity force and the distance it traveled
[tex]E_p = Ph = mgh = 6*9.81*13.35 = 786 J