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# Physics help: specific heat capacity watch

1. Doing some physics work and wanted to know what i would do for this question. This is probably the 100th time i've asked for clarification on a question....its ridiculous. Ok i'll stop rambling now!

' Calculate the energy needed to raise the temperature of 0.40kg of water in an aluminium container of mass 0.20kg from 15 degress to 40 degrees' btw the heat capacity is 900j/kg

Right.
I know the equation and everything but i was wondering if for the mass i just add the 0.40kg to the 0.20 kg to get my mass. Also for the temp i subtract 15 from 40 degrees. My main question is...do we add the masses? If not, why????

Thank You Xxxx
2. If you're raising the temperature of the water and the aluminium you should calculate the energy required to raise the temperature of the aluminium (SHC ~900) and the water (SHC ~4000) by the ΔT separately and then add them together.

or you could calculate a weighted average heat capacity of the combined Al and water based on their SHC and masses and use that.
3. (Original post by Joinedup)
If you're raising the temperature of the water and the aluminium you should calculate the energy required to raise the temperature of the aluminium (SHC ~900) and the water (SHC ~4000) by the ΔT separately and then add them together.

or you could calculate a weighted average heat capacity of the combined Al and water based on their SHC and masses and use that.
Ohhhh i seee! Thank you!!!! Xxx

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