Calculating Submarine Recoil Speed from Torpedo Launch

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In summary, the conversation discusses a submarine firing a torpedo and the calculation of the initial recoil speed of the submarine. The equation Pi=Pf is used to calculate the final momentum of the system, with the initial momentum of the submarine being 0. The final momentum is equal to the mass of the torpedo multiplied by its initial velocity, minus the mass of the submarine multiplied by its initial velocity. After performing the calculation, the initial recoil speed of the submarine is determined to be approximately 0.0114 m/s. The person asking the question initially thought they had the wrong answer, but later realized that their online homework system required a more precise answer.
  • #1
mikefitz
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A submarine of mass 2.3 times 106 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.

My work:

Pi=Pf
Pi=0
Pf= Mtorpedo * Vtorpedo - Msub * Vsub

Vsub = (260kg * (100.9 m/s) ) / 2.3 x 10^6

I get Vsub = .0114 m/s

Why is this wrong?? Thanks
 
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  • #2
Looks OK to me. Why do you think it's wrong?
 
  • #3
Stupid online homework system, I had to take the answer out a few more decimal places.

Thanks for your help Doc Al, appreciate it.
 

1. What is a submarine?

A submarine is a watercraft that is capable of operating completely submerged in water. It is designed to be used for military purposes, such as conducting underwater warfare and surveillance missions.

2. How does a submarine move underwater?

A submarine uses a propulsion system, typically a combination of diesel engines and electric motors, to move underwater. The diesel engines generate electricity, which is then used to power the electric motors that turn the propeller. Some submarines also use nuclear power as a source of propulsion.

3. What is a torpedo?

A torpedo is a self-propelled weapon that is designed to be launched from a submarine or other underwater vessel. It travels through the water and explodes upon impact, causing damage to enemy ships or other targets.

4. How does a torpedo work?

A torpedo is powered by an engine, usually an electric motor or a small rocket engine, which propels it through the water. It also contains sensors, such as sonar, to help guide it towards its target. Once it reaches its target, it explodes, causing damage to the target.

5. What are the main uses of submarines and torpedoes?

Submarines and torpedoes are primarily used for military purposes, such as attacking enemy ships, conducting surveillance and reconnaissance missions, and providing a strategic advantage in warfare. They can also be used for scientific research and exploration of the ocean depths.

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