Physics simplified!

Except in this example that isn’t accounted for.

What is important is the difference between the temperature of the object and the temperature of its surroundings.

Take two identical cups of hot tea, put one in the fridge and leave one on the table, after ten minutes which one is cooler?

Eh what? I could have told him that the cooling of a hot object slows as the area around it absorbs heat from the cooling object. When you think about it is obvious that has to happen.

Eh ?

Thanks guys. It makes sense now. The ironic thing is I could have told him that much.

The actual problem is quite simple; how long does it take an object to cool from one temperature 35°C to another 30°C.

(I can’t remember the exact numbers but I’m not going to sit through that again, sorry if I get them wrong but the principal still holds.)

The problem is complicated by the fact that an object cools at a different speed depending on how hot it is relative to its surroundings (in this case 20°C).

So as the object cools the speed that it cools changes too (rate-of-change) so the object will cool faster between 40°C and 35°C than it will between 35°C and 30°C.

Now if we know how long it takes for the object to cool between 40°C and 35°C, in this case 10 minutes, it is possible to calculate how long it will take to cool between 35°C and 30°C.

This is possible because nothing else about the object has changed, such as its mass or its surface area, so these things are constant (and are governed by the expression KA in the example).

The lecturer uses two methods to solve the problem, the first uses an average rate-of-change to get an answer (14 minutes), the second uses a more accurate method that uses calculus to get the answer (14.096 minutes, IIRC).

I would use the first method…..because I ******* hate calculus! 😡

Sure, here is the graph :

I just had to watch that in slow motion a couple of times to understand him!:D

The actual problem is quite simple; how long does it take an object to cool from one temperature 35°C to another 30°C.

(I can’t remember the exact numbers but I’m not going to sit through that again, sorry if I get them wrong but the principal still holds.)

The problem is complicated by the fact that an object cools at a different speed depending on how hot it is relative to its surroundings (in this case 20°C).

So as the object cools the speed that it cools changes too (rate-of-change) so the object will cool faster between 40°C and 35°C than it will between 35°C and 30°C.

Now if we know how long it takes for the object to cool between 40°C and 35°C, in this case 10 minutes, it is possible to calculate how long it will take to cool between 35°C and 30°C.

This is possible because nothing else about the object has changed, such as its mass or its surface area, so these things are constant (and are governed by the expression KA in the example).

The lecturer uses two methods to solve the problem, the first uses an average rate-of-change to get an answer (14 minutes), the second uses a more accurate method that uses calculus to get the answer (14.096 minutes, IIRC).

I would use the first method…..because I ******* hate calculus! 😡

Alright clever clogs, would you like to put it in simple terms us idiots can understand please?

Made perfect sense to me…..and his accent is easier to understand that one of my Thermodynamics lecturers, who was Korean. 😀

And you can take your time studyng the text book instead of trying to follow a tutor speaking a mile a minute on a formula which makes the subject mtter seem like a foreign language ( it is to me anyway) I was OK with chemistry but could never get on with physics. Probably because even though Chemistry can be taken to quite a high level before the maths thing gets really involved, with physics it is there even at a low level. I was never any good at maths but I have a head for numbers if that makes sense.

I had a tutor once like him! everything made sense till he tried to explain:) Some times a text book speaks volumes.

As my Mum would say As clear as mud. If anyone actually manages to figure it out I’d love them to explain it in a language I can understand.

:D:D It’s like trying to order a curry around these parts! Loops.:D