What to use when equations require mass but given a volume ?

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Discussion Overview

The discussion revolves around how to determine mass from a given volume when using equations that involve mass, specifically in the context of thermal energy calculations. Participants explore the relationship between density, volume, and mass, and how to apply these concepts in practical problems.

Discussion Character

  • Technical explanation, Mathematical reasoning, Homework-related

Main Points Raised

  • One participant questions whether it is valid to assume that 1 kg equals 1 L in the context of a specific problem involving thermal energy.
  • Another participant points out that the problem provides a volume of 1 L and a density of 1 g/cm³, prompting a discussion on the definition of density.
  • A participant states the formula for mass as Mass = Density x Volume and suggests converting density to kg/m³, noting that 1 g/cm³ is equivalent to 1000 kg/m³.
  • There is agreement that multiplying the converted density by the volume will yield the mass in kg.
  • One participant checks their calculations and concludes that the mass is 1 kg, leading to a calculation of time based on energy equations.
  • Another participant confirms the correctness of the calculations presented.

Areas of Agreement / Disagreement

Participants generally agree on the method of calculating mass from volume and density, but there is some uncertainty regarding the initial assumption of 1 kg equaling 1 L.

Contextual Notes

The discussion does not resolve the initial assumption about the equivalence of mass and volume, and it relies on specific definitions of density that may vary in different contexts.

CannonSLX
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In some questions, I've noticed that some questions which relate to equations that involve mass (Kg) and I am given a volume.

e.g
http://gyazo.com/169d40e27c5a14508724cb574635aca8

Know I that Δu=mCΔT, and I know that Δu=400w x t = m x 4200 x 60
and solve for t, but do I assumption that 1Kg = 1 L ?
 
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You were given the volume of 1 L and a density of 1 g/cm3.

What's the definition of density?
 
rock.freak667 said:
You were given the volume of 1 L and a density of 1 g/cm3.

What's the definition of density?
Mass = Density x Volume

So would I convert the density to kg/m3 which is basically x1000 ?
and so the volume is 0.001m3
 
Yes that's correct.

So you multiply the two and you get your mass in kg.
 
rock.freak667 said:
Yes that's correct.

So you multiply the two and you get your mass in kg.
Have I done the question correctly ? (ignoring units) Mass = 1kg
400xt=1x4200x60

So the time is 630 seconds ?
 
Yes that should be correct.
 
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