Newtons law of cooling

[lisafaustina]

Can somebody plz verify the formula?
Is it k(T-Ts) or -k(T-Ts)
Thanks  :smitten:

[sajib_mostofa]

It's if its cooling down

[cameron_15]

k is a constant, it shouldn't matter...

When the object is hotter than the surrounds, it will cool down, k will be negative.

When the object is colder than the surrounds, it will heat up, k will be positive.

either of those will get you the right answer, when you solve for k the calculus will take care of you. Having said that, I'd just run with k(T-Ts) for simplicity.

[sajib_mostofa]

But when you integrate, isn't the sign of k going to influence what expression you get?

[Martoman]

Not if you take it out of the integration.

[cameron_15]

Yes, but then when you evaluate k, it will also influence the expression you get.

So if you are using -k(T-Ts) but the object is heating up, the value of k (when evaluated) should be negative. ie -(-K)(T-Ts) = k(T-Ts)

[sajib_mostofa]

Ahh yes I see. Thanks