liquid cooling question

[morag]

hi,

this is my first post and an easy one for you all i would think. This question came up in another forum and the answer was given as b. Are there any views on this or is the answer in all cases option b.

 

Imagine you have just poured a freshly brewed cup of hot filtered coffee into your mug and just as you are about to pour in the milk the phone rings, it's the boss, he wants you to deliver some important papers, which is gonna take 4 or 5 minutes.

 

You want the coffee to be as hot as possible on your return

 

do you

 

( a ) leave the coffee in the mug without the milk (ready to add the milk on your return)

 

or

 

( b ) add the milk before you leave?

 

cheers,

 

morag

[insane_alien]

sounds more like a homework question to me. the answr is b because a cool(er) object will lose heat slower than a hot(ter) object

[m4rc]

For coffee, most people will put a little cold milk in a lot of hot coffee. Under these circumstances, after 5 minutes, the coffee will be warmer if the milk is added as soon as possible. This is because the higher the temperature of the cofee the faster it cools down. Mixing of the milk will cause a instantaneous drop in the temperature of the coffee. The coffee will then cool down slower than if no milk was added. This will be the answer if you put a little cold milk in your coffee. If you put lots of cold milk in your coffee (ending up with more milk than cofee), then (a) would be the answer.

[Klaynos]

For coffee, most people will put a little cold milk in a lot of hot coffee. Under these circumstances, after 5 minutes, the coffee will be warmer if the milk is added as soon as possible. This is because the higher the temperature of the cofee the faster it cools down. Mixing of the milk will cause a instantaneous drop in the temperature of the coffee. The coffee will then cool down slower than if no milk was added. This will be the answer if you put a little cold milk in your coffee. If you put lots of cold milk in your coffee (ending up with more milk than cofee), then (a) would be the answer.

 

 

I second this. due to the way the gradient of the curve of temperature drop changeds over time due to it cooling

[morag]

cheers folks..

 

that was the bit i was missing. I wanted to disprove that the answer would always be (b) - based on the original question and as it didn't specify the amount of milk to be added prior to leaving it then that is the basis for my disagreement with the blanket answer..

 

cheers

[swansont]

It also depends on the ambient conditions. Imagine it is insanely hot, being the middle of summer and the faulty air conditioning being on the fritz again (why you drink coffee under such conditions, I'll never know. You're apparently the crazy one at your company). If you wait, the milk will warm up a lot and the coffee cool only a little. So (a) could be the choice.