Momentum problem -- Forces on a human cannonball in a circus

[meso]

Homework Statement

3. Human cannonballs have been a part of circuses for years. A human cannonball with a mass of 70 kg experiences an impulse of 4.0x103 Ns for 0.35 s.
a) Calculate the force acting on the human 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.)
I sloved part a but I am stuck at b

Relevant Equations

p=mv
FnetΔt=Δp

P Total in= P Total fin

m1v1 Intial + m2v2intial= M1v1 final + m2v2 final
elastic collsion
P in= P final

P=Fnet x t that is what I used for a

 

[etotheipi]

What's the acceleration of the cannonball? I think it's assumed the force is constant (which is perhaps slightly unrealistic...), in which case what are the equations of motion for constant acceleration?

 

[meso]

What's the acceleration of the cannonball? I think it's assumed the force is constant (which is perhaps slightly unrealistic...), in which case what are the equations of motion for constant acceleration?

No acceleration provided. I do not know the equation for constant acceleration.

 

[etotheipi]

No acceleration provided.

You have the force from (a), and you know the mass. How then might we work out the acceleration?

I do not know the equation for constant acceleration.

Try searching for the 'suvat' equations. You should be able to find one which let's you calculate the length of the barrel when know the initial velocity, acceleration and time (which you do!).

 

[haruspex]

"an impulse of 4.0x103 Ns for 0.35 s."

That's a curious way to describe it. It's like saying a car is driven 50km for one hour.
You can have a force (here assumed constant) acting for a period, or an impulse spread over a period,