Conservation of linear momentum

Click For Summary

Homework Help Overview

The problem involves a runaway railroad car with a mass of 14,000 kg rolling horizontally at a speed of 4.00 m/s, which suddenly receives 2000 kg of grain. The grain leaks out at a rate of 10 kg/s, and the question focuses on the time taken for the car to cover a distance of 500 m.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the initial and final horizontal momentum of the car and the grain, questioning how the addition of grain affects the speed of the car. There are inquiries about the relationship between momentum before and after the grain drops, and the implications of the grain leaking out on the car's speed.

Discussion Status

Participants are exploring the relationship between the momentum of the car and the grain, with some guidance provided regarding the effects of external forces on the system. There is an ongoing examination of the implications of the grain leak on the car's motion, but no consensus has been reached.

Contextual Notes

Participants note the need for time to determine the speed of the car and grain after the drop, indicating that time is a critical variable in their calculations.

daivinhtran
Messages
68
Reaction score
0

Homework Statement


A runaway 14,000 kg railroad car is rolling horizontally at 4.00 m/s toward a switchyard. As it passes by a grain elevator, 2000 of grain suddenly drops into the car. Suppose the there is a small vertical chute in the bottom of the car so that the grain leaks out at 10 kg/s. How long does it take the car to cover 500m


Homework Equations


Pi = Pf



The Attempt at a Solution


Picture attached
 

Attachments

Physics news on Phys.org
daivinhtran said:

Homework Statement


A runaway 14,000 kg railroad car is rolling horizontally at 4.00 m/s toward a switchyard. As it passes by a grain elevator, 2000 of grain suddenly drops into the car. Suppose the there is a small vertical chute in the bottom of the car so that the grain leaks out at 10 kg/s. How long does it take the car to cover 500m


Homework Equations


Pi = Pf



The Attempt at a Solution


Picture attached
What is the initial horizontal momentum of the car and how does that relate to the horizontal momentum of the car + grain after the grain drops? Can you determine the speed of the car + grain after the drop? What effect does the vertical leak of grain have on the horizontal speed of the car?

AM
 
Andrew Mason said:
What is the initial horizontal momentum of the car and how does that relate to the horizontal momentum of the car + grain after the grain drops? Can you determine the speed of the car + grain after the drop? What effect does the vertical leak of grain have on the horizontal speed of the car?

AM

I already included those in my paper (attached).
However I can't determine the speed of the car + grain after drop unless I know the time.
 
daivinhtran said:
I already included those in my paper (attached).
However I can't determine the speed of the car + grain after drop unless I know the time.
Sure you can. How does the horizontal momentum before the collision compare to the horizontal momentum after the collision? (hint: are there any forces acting in the horizontal direction that are external to the car - grain system?).

AM
 
Andrew is asking what the speed is immediately after the drop, i.e. t = 0.
Separately, he asks what affect the grain leak has on the car thereafter.
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
Replies
7
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 17 ·
Replies
17
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
Replies
8
Views
12K