Engineering Board Exam Reviewer · Thermodynamics · hard

An automobile tire has a gauge pressure of 200 kPa at 25 °C. After driving, the temperature of the air rises to 50 °C. Assuming constant volume and atmospheric pressure of 101.325 kPa, what is the new gauge pressure? (Use K = ° C + 273)

  1. 400.00 kPa
  2. 216.78 kPa
  3. 225.28 kPa
  4. 326.60 kPa

Answer

C. 225.28 kPa

Solution

Use absolute values: P1 = 301.325 kPa. P2 = P1(T2/T1) = 301.325(323/298) = 326.60 kPa abs gauge = 326.60 - 101.325 = 225.28 kPa.

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