First of all, we can find the kinetic energy of the human cannonball when he leaves the barrel. It is
[tex]K= \frac{1}{2}mv^2= \frac{1}{2}(80 kg)(15 m/s)^2 = 9000 J [/tex]
This kinetic energy is equal to the work done by the cannon on the human, which is
[tex]W=F d[/tex]
where d=9 m is the length of the barrel, and F is the net force applied. Since K=W, we can find the value of F:
[tex]F= \frac{W}{d}= \frac{K}{d}= \frac{9000 J}{9 m}=1000 N [/tex]
