Relating Kinetic Energies and Masses of Two Objects

  • Thread starter Thread starter B3NR4Y
  • Start date Start date
  • Tags Tags
    Energies Kinetic
Click For Summary

Homework Help Overview

The discussion revolves around the relationship between the kinetic energies of two objects with masses m1 and m2 that start from rest and interact with each other. The original poster is attempting to find the ratio of their kinetic energies at any instant, given their velocities and masses.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to express the ratio of kinetic energies in terms of the masses, having derived a relationship between their velocities. Some participants question the correctness of the original poster's answer and the method used to arrive at it.

Discussion Status

The discussion is ongoing, with participants expressing uncertainty about the correctness of the original poster's answer. There are indications that the original poster is receiving mixed feedback, with some suggesting that the answer is correct while others express doubt. The mention of a new system potentially causing errors adds complexity to the situation.

Contextual Notes

The original poster notes that the problem is part of a homework assignment and that the grading system may have inconsistencies, as indicated by their professor. This context suggests that there may be external factors influencing the discussion.

B3NR4Y
Gold Member
Messages
170
Reaction score
1

Homework Statement


Two objects of inertias m1 and m2 start from rest and then interact with each other (assume neither is interacting with any other object).
What is the ratio of their kinetic energies at any instant?

Homework Equations


\frac{K_{1}}{K_{2}} = ?
The first part of the equation asked me to relate velocities to masses and I got a correct answer of

\frac{v_{2x}}{v_{1x}} = -\frac{m_{1}}{m_{2}}

The Attempt at a Solution


I know that Kinetic Energy is half of the mass times the square of the velocity, and that's where my attempt falls apart, because I have to express the answer in terms of m1 and m2, but they're already in KE so I don't understand how that works out. My answer I got was

\frac{K_{1}}{K_{2}} = \frac{m_{2}}{m_{1}}

Without the negative cause it is the square of the velocity and that will eliminate any negatives. Please help.
 
Physics news on Phys.org
So what is your question?
The answer looks OK.
 
nasu said:
So what is your question?
The answer looks OK.

It's not okay though :( apparently I am not correct :mad:
 
The answer you have obtained is correct .
 
B3NR4Y said:
It's not okay though :( apparently I am not correct :mad:

How do you know this? What do you think is the correct answer?
 
nasu said:
How do you know this? What do you think is the correct answer?

It's part of a homework assignment and when I put in an answer it spits out a correct or incorrect judgement. I put in my answer and it's incorrect. The professor said things like this would happen though, and when they did to come to him because we're using a new system and there are mistakes in it that he's found. I hope that is the case because I tried every combination of subscript and now they most I can get on the question is 50% for a correct answer regardless of the amount of tries.
 

Similar threads

Replies
21
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
10
Views
3K
Replies
9
Views
966
  • · Replies 3 ·
Replies
3
Views
550
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
15
Views
2K
  • · Replies 15 ·
Replies
15
Views
4K