# Silly basic E = mct question

This is probably a dumb question but, when calculating E = mct, if mass is in g, then c should be in J/g·°C right? Similarly, if mass is in kg, then c should be in J/kg°C? If i mix any of them up and do m in g and c in j/kg then my answer would be off right?
thanks!

(this is my first post, i wasnt sure if it goes in the homework thread since it's not a specific problem)

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Andrew Mason
Homework Helper
This is probably a dumb question but, when calculating E = mct, if mass is in g, then c should be in J/g·°C right? Similarly, if mass is in kg, then c should be in J/kg°C? If i mix any of them up and do m in g and c in j/kg then my answer would be off right?
thanks!

(this is my first post, i wasnt sure if it goes in the homework thread since it's not a specific problem)
Welcome to PF.

You should keep your units in the same system. You cannot use cgs (centimetres, grams, seconds) units interchangeably with MKS units (metres, kilograms, seconds). You have to convert.

A Joule is a measure of energy in MKS units. A Joule is one Newton x 1 metre. Since a Newton is 1 kg x 1 m/sec^2, a Joule is also 1 kg x 1 (m/sec)^2.

So if you are trying to find $\Delta Q = mC\Delta T$ in Joules but you are given the heat capacity Joules/gram, and mass in kilograms, convert c to Joules/kg before plugging the value in.

AM