Physics Problem: Center of Mass

In summary, a spaceship with its engines off and carrying rockets fires a rocket straight ahead at an enemy vessel. The rocket has a mass of 1200 kg and brings the spaceship to a halt. Using the conservation of momentum, the velocity of the rocket can be calculated by setting the initial and final momentum of the center of mass equal to each other. This is equivalent to using the formula vcm=(m1*v1+m2*v2)/(m1+m2). However, this formula does not take into account external forces, which may lead to an incorrect answer.
  • #1
shawonna23
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0
With the engines off, a spaceship is coasting at a velocity of +250 m/s through outer space. The ship carries rockets that are mounted in firing tubes, the back ends of which are closed. It fires a rocket straight ahead at an enemy vessel. The mass of the rocket is 1200 kg, and the mass of the spaceship (not including the rocket) is 2.0 106 kg. The firing of the rocket brings the spaceship to a halt. What is the velocity of the rocket?

I used the equation vcm=(m1*v1+m2*v2)/(m1+m2) but the answer I got is wrong. Please help ASAP!
 
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  • #2
The idea is that whole of the momentum of the ship is transferred to the rocket.

Just use the conservation of momentum. The momentum which was shared by both the rocket and ship before is now with the rocket alone.

This will tell you the rocket's velocity.

spacetime
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  • #3
shawonna23 said:
I used the equation vcm=(m1*v1+m2*v2)/(m1+m2) but the answer I got is wrong.
This formula calculates the velocity of the center of mass (CM) of the system. That velocity does not change. If you wanted to apply this to the problem, you'd calculate the velocity of the CM before and after, and set them equal. Do it and you'll see that is equivalent to applying conservation of momentum.

Please do not double post!
 
Last edited:

1. What is the definition of center of mass?

The center of mass is the point at which the mass of an object or system is concentrated and can be treated as a single point for the purpose of calculating its motion.

2. How is the center of mass calculated?

The center of mass is calculated by taking the weighted average of the positions of all the particles in the object or system, with the weights being the masses of the particles.

3. Why is the center of mass important in physics?

The center of mass is important because it allows us to understand and predict the motion of objects and systems. It also helps in determining the stability of objects and analyzing collisions.

4. How does the center of mass change when objects are moved or rearranged?

The center of mass will change when objects are moved or rearranged, as the positions and masses of the particles are altered. However, if the external forces acting on the system are balanced, the center of mass will remain in the same position.

5. Can the center of mass be located outside of an object?

Yes, the center of mass can be located outside of an object. This is common in irregularly shaped objects where the distribution of mass is not symmetrical.

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