How this unit comes like that ?

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Homework Help Overview

The discussion revolves around the derivation and understanding of the unit for the specific gas constant, R, expressed as kJ/(kg*K). Participants are exploring the relationship between specific volume, pressure, and temperature in the context of thermodynamics.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to understand how the unit kJ/(kg*K) is derived from the equation involving specific volume, pressure, and temperature. Some are questioning their own calculations and expressing confusion about unit conversions.

Discussion Status

There is an ongoing exploration of the units involved, with some participants providing insights into the relationships between Joules, Newtons, and the dimensions of the variables. Guidance has been offered to show calculations to identify potential errors in understanding.

Contextual Notes

Participants are grappling with the clarity of unit representation and the implications of using different symbols in their calculations. There is a noted ambiguity in the notation used for units, which may affect understanding.

manal950
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How this unit comes

R = specific volume X (pressure / Temperature )

0.9m^3/kg (1.3X10^5 N/m^2 / 408 K )

R = 286 KJ/KgK

please can anyone explain to me how the unit ( KJ/KgK ) comes ??
 
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kJ/(kg*K) - looks quite straightforward, where is the problem?
 
Hi sir .. I know the unit is correct but when I try to solve by my self I don't get that uint

please help ..
 
r = volume * pressure / temperature
= (length*length*length)/mass * Newtons/(length*length) / temperature
= length*Newtons/(temperature * mass)

= Joules/(temperature * mass)
 
manal950 said:
Hi sir .. I know the unit is correct but when I try to solve by my self I don't get that uint

Show what you did then and we will try to find out where did you get wrong.
 
1 Joule = 1 N-m
 
Chestermiller said:
1 Joule = 1 N-m

Dash that looks like a minus is not the luckiest selection of the symbol in this context.

1 Joule = 1 Newton * m

is much less ambiguous.
 

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