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    hi
    really cant seem to work this question out:

    at the start of a journey the temp and pressure inside a car tyre were 17 degrees and 300kPa.during the journey the pressure was 350kPa
    calculate the temp during the journey :confused:

    thanx
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    hey pls cmon ppl!!!
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    Is the volume of the gas Constant?
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    is doesnt actually say..but i reckon it should be coz its inside a car tyre.. :confused:
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    Remember the relationship between pressure and temperature, p = kT, therefore p/T = k, so p1/T1 = p2/T2

    To work out T2 therefore you have p2T1/p1, so in this case:

    (350 * 17) / 300 = 20 degrees (to 2 significant figures)

    (it is ok to leave the pressures as kPa etc because both of them use the same units).
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    P1V1/T1 = P2V2/T2, but V1=V2, so P1/T1 = P2/T2, so T2 = P2T1/P1

    Where P2 = 350,000
    P1 = 300,000
    T1 = 17+273 (It should be in Kelvin)
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    Don't forget though that the temperature must be converted into Kelvins first i think.
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    (Original post by Rebuke)
    Remember the relationship between pressure and temperature, p = kT, therefore p/T = k, so p1/T1 = p2/T2

    To work out T2 therefore you have p2T1/p1, so in this case:

    (350 * 17) / 300 = 20 degrees (to 2 significant figures)

    (it is ok to leave the pressures as kPa etc because both of them use the same units).

    thanx sooooo much 4 ure help im still kinda confused as to how u rearraged the formula to find T2=p2*T1/p1
    sorry im jus kinda slow....
    xxxx
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    Oops, you're right, temperature does have to be converted into Kelvin first so the answer I gave is wrong

    As for re-arranging it, you take p = kT, divide by T to get p/T = k

    Now, assuming the volume doesnt change, that k will be the same in both circumstances, so if you have the two sets of values you can show that p1/T1 = k and p2/T2 =k, i.e. p1/T1 = p2/T2

    Then multiply by T2 to get p1T2/T1 = p2, divide by p1 to get T2/T1 = p2/p1, then multiply by T1 to get T2 = p2T1/p1

    Now, the bit I forgot as pointed out by Willa and female_engineer is that you have to convert the temps into Kelvin first by adding 273 to them, so 17 degrees C = 290 degrees kelvin

    Now you get (350 * 290) / 300 = 338 degrees Kelvin, now subtract 273 to get degrees C and you get 65 degrees C (to 2 significatn figures).
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    hey thanx alot guyz
    really appreciate ure help!!
 
 
 

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