Solving Physics Problem: Momentum of mK Affected by mL

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Homework Help Overview

The discussion revolves around a physics problem involving momentum and the effects of gravitational potential energy on two masses, mK and mL. The original poster presents a scenario where mass mL is dropped from a height of 18 meters, and participants are tasked with determining the momentum affecting mass mK. The problem context includes specific values for the masses and notes that there is no friction.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Some participants suggest using energy conservation principles to analyze the problem. Others question whether this approach is valid without knowing the gravitational acceleration of the system. There is also discussion about the implications of the problem potentially not being set on Earth, which raises concerns about the given answer.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. There is no explicit consensus on the validity of the assumptions made regarding gravity, and some participants are seeking clarification on the problem statement itself. Guidance has been offered to consider mechanical energy conservation, but the lack of information about gravity remains a point of contention.

Contextual Notes

Participants note that the problem does not specify the gravitational context, leading to uncertainty about the applicability of standard gravitational values. The original poster expresses confusion about the provided answer, suggesting a potential error in the problem statement or answer key.

BerkS
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Hey everybody,
there's one little problem I've been working on for hours now, I'm usually not that bad however I couldn't imagine how to solve this using the given Information:

1. Given Statement
mK=3kg
mL=2kg
There's no friction
-L is dropped without any speed, after falling 18 meters, what is the momentum(impuls? or sorry what ever it is lol..) affecting K in Newton.seconds

Sorry for the bad English, thanks for the help

https://docs.google.com/open?id=0B6PkUjlHR5ahaUtDQmZCWHFLR0U


Homework Equations


1/2at^2=x
mV=P
F.Δt=m.ΔV


The Answer is given as 9, though I couldn't formulate it into anything
 
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Why not try energy conservation?
 
Doc Al said:
Why not try energy conservation?

Is that possible without knowing the gravity of the system? If yes then how?
 
BerkS said:
Is that possible without knowing the gravity of the system?
What do you mean by "knowing the gravity" of the system? Isn't it on Earth with normal gravity?
If yes then how?
Mechanical energy is conserved. (Look up mechanical energy and conservation of energy.)
 
Doc Al said:
What do you mean by "knowing the gravity" of the system? Isn't it on Earth with normal gravity?

I'll try it again with conservation of energy, but no it's not necessarily on Earth.
 
BerkS said:
I'll try it again with conservation of energy, but no it's not necessarily on Earth.
If it's not on earth, I don't see how you can solve the problem. Not enough information.

Can you state the problem word for word as it was given? (What makes you think it's not on earth?)
 
Doc Al said:
If it's not on earth, I don't see how you can solve the problem. Not enough information.

Can you state the problem word for word as it was given? (What makes you think it's not on earth?)

In a system in which friction is unimportant, the bodies K and L are released. When body L has dropped 18 meters, what is the Impuls given K in kg.m/(s^2).s=N.s

I assume it's not on Earth because if it was the result couldn't be 9, and the book the question is from usually states the gravity either as 9.8 or (in some questions) 10.
 
Last edited:
BerkS said:
In a system in which friction is unimportant, the bodies K and L are released. When body L has dropped 18 meters, what is the Impuls given K in kg.m/(s^2).s=N.s
OK, clear enough.

I assume it's not on Earth because if it was the result couldn't be 9, and the book the question is from usually states the gravity either as 9.8 or (in some questions) 10.
I agree that the answer cannot be 9, but I suspect that's just an error in your problem statement or answer key. Unless they tell you otherwise, I would assume the set up is on Earth!

Show how you would solve the problem and then we can see if you're on the right track or not, regardless of the given answer.
 

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