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.

Question

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.)

Answer 1

average Force = change of momentum / time = impulse / time
a) F = 4.0*10^3 / 0.35 Newtons
b) momentum at start = 0
momentum at end = 4*10^3
average momentum during trip up barrel = 2*10*3
average velocity in barrel = 2*10^3 / 70 = 28.6 m/s
28.6 m/s * 0.35 s = 10 meters long

Answer 2

Why is the initial momentum at zero?

Answer 3

The initial momentum is at the base of the barrel when you explode the gunpowder. It is not moving until the explosion. It accelerates up the barrel.

Answer 4

Of course with a human you might not use gunpowder :) However you would fake it with a big spring and some smoke I suppose.

Answer 5

Thank you ;-)