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 Homework Statement

A cannonball with a mass of 70 kg experiences an impulse of 4.0 x 10^3 N*s for 0.35 s
a) calculate the force acting on the cannonball
b) How long was the barrel of the cannon?. Assume the force is applied only for the period of time that the cannonball is in the cannon.
 Homework Equations

J = Ft
W= Fd
J = mv'  mv
a)
F = J/t
F = 4000 N*s / 0.35 s
F = 11429 N
b) I was going to equate impulse to the change in momentum and solve for v' (final velocity). Then use v' to solve for ΔEk. set ΔEk = Fd and solve for d. (The question never mentioned an angle of inclination, so I thought it would be ok to use W = Fd)
However when I was isolating v' I realized I wasn't sure what v (initial velocity) was. Is it 0 m/s?
I can solve for Δv using J = ΔP = mΔv (right?) But I'm not sure what I could do with that without knowing either the initial or final velocity. Basically, I'm not sure whether I can use 0 m/s for initial velocity or not.
F = J/t
F = 4000 N*s / 0.35 s
F = 11429 N
b) I was going to equate impulse to the change in momentum and solve for v' (final velocity). Then use v' to solve for ΔEk. set ΔEk = Fd and solve for d. (The question never mentioned an angle of inclination, so I thought it would be ok to use W = Fd)
However when I was isolating v' I realized I wasn't sure what v (initial velocity) was. Is it 0 m/s?
I can solve for Δv using J = ΔP = mΔv (right?) But I'm not sure what I could do with that without knowing either the initial or final velocity. Basically, I'm not sure whether I can use 0 m/s for initial velocity or not.