Change In Tyre Air Pressure

[slocjo]

hello...CAN SOMEONE PLEASE TELL ME A ANSWER TO A QUESTION I HAVE..HOW MUCH DOES TYRE AIR PRESSURE CHANGE WITH THE TEMPERATURE (A) APPROX 0.2BAR/15C (B) APPROX 0.1BAR/15C (C) APPROX 0.1BAR/10C (D) APPROX 0.2BAR/ 10C Advance thanks..

[Zacs-Master]

Your question has a lack of data or parameters such as:
Temperature increase or decrease
The range of temperature you are talking about (from/to)
Size of tyres in question
Whether the vehicle is static or in motion (or a combination)
What the starting pressure is and whether it is standard for that tyre

[bhg481]

Zacs, I think you've misunderstood the question but there is still data missing.
I think the question is a multiple choice and you have to choose the correct answer from the 4 given.
Let's assume that the tyre is a normal car tyre, starting temp 20deg (=293 Kelvin) at a pressure of about 30psi = 2 bar and that the volume of the tyre doesn't change with increase in pressure.

We can now use Gay-Lussac's Law p1/T1 = p2/T2

p2 = (p1 x T2)/T1

for a 15 deg increase in temp we get p2 = (2 x 308)/293 = approx 2.1bar

the increase in pressure
is 2.1 - 2.0 = 0.1 bar for a 15 deg increase in temp.

Now see which of these options this agrees with and there's your answer.

[slocjo]

Hello..sorry to you both ref. data.but that's how it was given.also the question (which I did,nt say) is truck related But I see bhg481 has come up with the right formula, well It ties up with one of the answers..so I go with that..thanks..

[bhg481]

Fine, but do you understand why?

[slocjo]

no I don't understand .but for all I know you could be taking the *** but that's fine by me, your answer ties up so its good for me..needs to be in by tomorrow...

[Peter Pedant]

.

Oh I did differentials at const V - so dP = k.dT - and ICs kay has to be 2/273

but in view of his answer I think I will keep quiet

[bhg481]

Certainly not taking th **** slocjo. I just hoped I could tech you the maths.

[Peter Pedant]

No he is truthing Slocjo

The answer is good - I checked with a different way - just for fun and got the same figure.