Calorie Joule and mass

  • Thread starter Quarlep
  • Start date
  • #1
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Lets suppose we have 2000 kcal and we want to translate it joule.
1 calorie is 4,2 J/gC isnt it so I think it will be 8400000 g m^2/s^2 But my teacher says its 8400000 kg m^2/s^2
Which one is true
Thanks
 

Answers and Replies

  • #2
257
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Note: Here (4,2 J/gC) J is joule g is grams and C is celcius
 
  • #3
jtbell
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1 calorie is 4,2 J/gC isnt it
No, 1 cal = 4.2 J (to one decimal place).

You're thinking of the specific heat of water, which is 4.2 J/(g·°C) = 1 cal/(g·°C).
 
  • #4
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Then let me clear Q=mcT and W=mgh so If we takes m we get Q/cT=W/gh If we write the unit form cal cal^-1 g C^-1 C we get g which it grams
and the other side kg m^2 s^-2 s^2 m^-1 m^-1 then we get kg.It does not match.and I think its a problem
 
  • #5
jtbell
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You're getting grams for the m from the first equation because you're using the specific heat per gram. Use the specific heat per kilogram instead: 4200 J/(kg·°C).
 
  • #6
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Thanks I understan it
 

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