# Simple thermodynamics

## Homework Statement

6. Cameron burns a 0.5g peanut beneath 75g of water, which increases in temperature from 22 ºC to 40 ºC
a. Assuming 40% efficiency, what is the food value, in J, of the peanut?
b. What is the food value in J per gram?

q=mCt

## The Attempt at a Solution

i just wanted to know does question a mean i take 40% from the calculated joules???

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No, it's not, what it's saying to you is that the energy given off by the peanut to heat up the water is only 40% of the total energy given off in combustion, you need to work out the 100%. (was confused there for a sec :D)

No. It means only 40% of the peanut's energy goes into the water

what so how am i meant to calulate the other 60% thats not possible???

Of course it's possible, that's like me saying to you;

You have 4 apples, which is 40% of the total number of apples from the bag, how many apples were in the bag?

er could you put that to me algerbarically please... i mean it makes sence if it was 50% all you do is double it

could it be .4x=(Joules calulated)???

0.0

From 50% to 100% you times by 2....

From 40% to 100% you times by...

And ^ yes you're right.

Of course it's possible, that's like me saying to you;

You have 4 apples, which is 40% of the total number of apples from the bag, how many apples were in the bag?
Beat me to it again.