Momentum problem (should be pretty easy I think)

  • Thread starter KatieLynn
  • Start date
  • #1
65
0

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 thats not right. First question is do you have to convert 20 metric tons to kilograms?
 

Answers and Replies

  • #2
PhanthomJay
Science Advisor
Homework Helper
Gold Member
7,167
507

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 thats not right. First question is do you have to convert 20 metric tons to kilograms?
did you put in the units for its speed?
 
  • #3
65
0
you mean 50 m/s yeah?...if thats not what you mean then I'm confused
 
  • #4
PhanthomJay
Science Advisor
Homework Helper
Gold Member
7,167
507
you mean 50 m/s yeah?...if thats 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.
 

Related Threads on Momentum problem (should be pretty easy I think)

Replies
3
Views
4K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
5
Views
4K
Replies
10
Views
7K
Replies
4
Views
7K
  • Last Post
Replies
1
Views
2K
Replies
18
Views
3K
Replies
3
Views
1K
  • Last Post
Replies
7
Views
2K
Top