Momentum problem (should be pretty easy I think)

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Homework Help Overview

The discussion revolves around a momentum problem involving a train's speed and its relationship to momentum. The original poster presents a scenario where a train's mass and initial velocity are given, and they seek to determine the speed required for the train to achieve double its original momentum.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants explore the relationship between mass, velocity, and momentum, with one participant questioning whether the mass needs conversion to kilograms. There is also a discussion about the correct interpretation of the initial speed and whether doubling the speed is the correct approach to find the new momentum.

Discussion Status

The discussion is ongoing, with participants clarifying the initial conditions and exploring different interpretations of how to achieve the desired momentum. Some guidance has been offered regarding the relationship between mass and velocity, but no consensus has been reached on the correct approach.

Contextual Notes

There is a mention of potential unit conversion for the mass of the train, which may affect the calculations. Additionally, participants are checking the accuracy of the initial speed provided in the problem statement.

KatieLynn
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Homework Statement



A 20 metric ton train moves toward the south at 50 m/s. What speed must it travel to have two times its original momentum?

Homework Equations



Change in momentum = mass(FinalVelocity - InitialVelocity)

The Attempt at a Solution



so I thought you would simply times 50 by 2 and get 100 to be the answer, but that's not right. First question is do you have to convert 20 metric tons to kilograms?
 
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KatieLynn said:

Homework Statement



A 20 metric ton train moves toward the south at 50 m/s. What speed must it travel to have two times its original momentum?

Homework Equations



Change in momentum = mass(FinalVelocity - InitialVelocity)

The Attempt at a Solution



so I thought you would simply times 50 by 2 and get 100 to be the answer, but that's not right. First question is do you have to convert 20 metric tons to kilograms?
did you put in the units for its speed?
 
you mean 50 m/s yeah?...if that's not what you mean then I'm confused
 
KatieLynn said:
you mean 50 m/s yeah?...if that's not what you mean then I'm confused
No, I meant 100m/s. In order for the momentum vector to be twice its original momentum, the new momentum must have a magnitude of twice as much and a direction in the same direction as the original momentum vector. Since its momentum doubles, and the mass is constant, then its velocity must double. So the velocity is 100m/s south. The speed is 100m/s. Unless we both missed something.
 

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