Physics Submarine Question?

Question

Physics Submarine Question?
A submarine of mass 2.1 *10^6 kg and initially at rest fires a torpedo of mass 260 kg. The torpedo has an initial speed of 100.9 m/s. What is the initial recoil speed of the submarine? Neglect the drag force of the water.

Answer 1

Ok, here you have to remember, that the linear momentum is the same before and after, the submarine fires the torpedo :

Then :

M*V = m*v'

M = mass of the submarine

m = mass of the torpedo

V = velocity of the submarine

v' = velocity of the torpedo

2.1*10^6*v = 260*100.9

v = 0.012 m /s

Hope that might help you.

Answer 2

Vs = Mt*Vt/Ms = 260*100.9/2.1E6 = -.0125 m/s