Gohanchi Posted August 24, 2012 Share Posted August 24, 2012 Hey Im having a bit of trouble with this homework. Can someone please help me with this. A vehicle makes a long journey. Before leaving, the driver checks the pressure of all the tyres using a tyre pressure gauge. The inner volume of each tyre is 30 litres and the indicator on the tyre pressure gauge reads 235kPa (about 34.1 psi). This is the safe operating pressure for these types of tyres. At the time of departure, the local weather forecast indicates the ambient temperature is at 25°C and the atmospheric pressure is 101.325kPa. At the end of the journey, the driver stops to inspect the tyres and finds the average temperature of the tyres is now at 50°C. a) Calculate the absolute pressure of air inside the tyre at the start of the journey (units kPa)? b) What is the mass of air in each tyre at the start of the journey (units kg)? c) What is the expected new (absolute) pressure in each tyre at the end of the journey (units kPa)? d) If the driver needs to bring back the gauge pressure to its original value, what mass (units grams) of air must be released from each tyre (at 50°C) in order to bring each tyre back to its safe operating pressure. Link to comment Share on other sites More sharing options...
CaptainPanic Posted August 24, 2012 Share Posted August 24, 2012 Since this is homework, we don't give straight answers. Which kind of formula do you think you will need? (Either write the formula, or give the name of the formula, if you know it). The more you show us that you tried yourself, the more we will help you. Link to comment Share on other sites More sharing options...
guyph Posted August 28, 2012 Share Posted August 28, 2012 Hi, I need help with this too. For the first question is the formula p=F/A? Link to comment Share on other sites More sharing options...
CaptainPanic Posted August 28, 2012 Share Posted August 28, 2012 Hi, I need help with this too. For the first question is the formula p=F/A? Well, that's a formula for pressure... but in all fairness, I think you'd better study a little more. There is no force (F) given, and no surface area (A) either... so your formula is not exactly useful here. Link to comment Share on other sites More sharing options...
Gohanchi Posted August 29, 2012 Author Share Posted August 29, 2012 the formula for Q1 is Pgage = Pabs - Patm 1 Link to comment Share on other sites More sharing options...
swansont Posted August 29, 2012 Share Posted August 29, 2012 the formula for Q1 is Pgage = Pabs - Patm So what happens when you apply this to the problem? Link to comment Share on other sites More sharing options...
guyph Posted September 2, 2012 Share Posted September 2, 2012 Pgage = Pabs - Patm 235=Pabs - 101.325 Pabs=235+101.325 =336.325kPa Is this right then? Link to comment Share on other sites More sharing options...
swansont Posted September 2, 2012 Share Posted September 2, 2012 Looks good to me. Link to comment Share on other sites More sharing options...
guyph Posted September 3, 2012 Share Posted September 3, 2012 Any help on the next parts? Link to comment Share on other sites More sharing options...
ACUV Posted September 4, 2012 Share Posted September 4, 2012 The assumption is of an ideal gas. Do you know any of the forms of the ideal gas formula in SI units ? There are a few which can be used based on the information you have and the information you want to get. Do you know the pressure in the tyre in SI units ? ..................................... N / ( M^2 ) ...................................... Newton per square Metre Do you know the volume of air in the tyre in SI units ? ................................................. ( M^3 ) ............................................ Cubic Metre Do you know the temperature of the air in the tyre in SI units ? ................................................... K ............................................ Kelvin Do you know the specific gas constant for air in SI units ? Thus Calculate the mass in Kilograms ! Link to comment Share on other sites More sharing options...
rameez Posted September 11, 2012 Share Posted September 11, 2012 Hey Im having a bit of trouble with this homework. Can someone please help me with this. A vehicle makes a long journey. Before leaving, the driver checks the pressure of all the tyres using a tyre pressure gauge. The inner volume of each tyre is 30 litres and the indicator on the tyre pressure gauge reads 235kPa (about 34.1 psi). This is the safe operating pressure for these types of tyres. At the time of departure, the local weather forecast indicates the ambient temperature is at 25°C and the atmospheric pressure is 101.325kPa. At the end of the journey, the driver stops to inspect the tyres and finds the average temperature of the tyres is now at 50°C. a) Calculate the absolute pressure of air inside the tyre at the start of the journey (units kPa)? b) What is the mass of air in each tyre at the start of the journey (units kg)? c) What is the expected new (absolute) pressure in each tyre at the end of the journey (units kPa)? d) If the driver needs to bring back the gauge pressure to its original value, what mass (units grams) of air must be released from each tyre (at 50°C) in order to bring each tyre back to its safe operating pressure. Link to comment Share on other sites More sharing options...
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