Initial velocity (and momentum)

Click For Summary

Homework Help Overview

The discussion revolves around a collision problem involving two cars of different masses and velocities, specifically focusing on the conservation of momentum in a moving reference frame.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to calculate the initial momentum in a reference frame moving at 10.0 m/s and questions the resulting value. Participants explore the initial and final velocities and momenta of both cars in this new frame.

Discussion Status

Participants are actively engaging with the problem, checking assumptions about momentum calculations and discussing the implications of the moving reference frame. Some guidance has been offered regarding the summation of momenta, and there is a recognition of momentum conservation.

Contextual Notes

There is an ongoing exploration of how the reference frame affects the perceived velocities and momenta of the cars involved in the collision. The discussion reflects uncertainty about the initial conditions and calculations in the new frame.

shiri
Messages
85
Reaction score
0
A 2020kg car moving at 20.0m/s collides and locks together with a 1400kg car at rest at a stop sign. Show that momentum is conserved in a reference frame moving at 10.0m/s in the direction of the moving car.

initial momentum

final momentum


I don't understand why that the answer for initial momentum is not 20200 kg*m/s due to a reference frame moving at 10.0m/s in the direction of the moving car. Can anyone help me out here, that will be awesome
 
Last edited by a moderator:
Physics news on Phys.org
In that new reference frame, what's the initial velocity (and momentum) of the 1400 kg car?
 
Last edited by a moderator:
Doc Al said:
In that new reference frame, what's the initial velocity (and momentum) of the 1400 kg car?

was it 10.0m/s and 14000kg*m/s in the opposite direction?
 
Exactly.
 
then do I have to sum it together (20200+ (-14000))kg*m/s? and the answer should be 6200kg*m/s for the initial momentum?
 
That's correct.
 
is that mean the final momentum is also 6200kg*m/s?
 
shiri said:
is that mean the final momentum is also 6200kg*m/s?
Sure. Momentum is conserved.
 
thanks Doc Al
 

Similar threads

Ambiguous question on momentum and how it works...
  • · Replies 13 ·
Replies
13
Views
1K
Final Velocity of a car with a opposing decreasing drag force
  • · Replies 57 ·
2
Replies
57
Views
3K
Golf club 🏌️and ball ⛳ impulse problem
  • · Replies 19 ·
Replies
19
Views
3K
Super Basic Collision Problem - Preparation for SR
  • · Replies 10 ·
Replies
10
Views
2K
Momentum in a perfectly inelastic collision
  • · Replies 6 ·
Replies
6
Views
2K
State whether the distance x for the block would be greater/less/same
  • · Replies 25 ·
Replies
25
Views
2K
Momentum, collision of two cars problem
  • · Replies 5 ·
Replies
5
Views
6K
Cars Collide on a Hill, Conservation of Momentum
  • · Replies 7 ·
Replies
7
Views
3K
Momentum in different referance frames
  • · Replies 6 ·
Replies
6
Views
2K
Solving the Elastric 3-Body Collision Problem
  • · Replies 2 ·
Replies
2
Views
3K