Answer the following questions regarding the measurement of fluid pressure:
(i) Define absolute pressure and gauge pressure.
(ii) Atmospheric pressure at a particular coastal city during a cyclone drops to 990hPa. A barometer at the same place normally reads 1.013×105Pa. Explain why the barometer reading falls during the cyclone.
(iii) For the atmospheric condition in part (ii), a tyre that had an absolute pressure of 2.50bar before the cyclone still contains the same quantity of air at the same temperature during the cyclone. Determine its gauge pressure during the cyclone.
(iv) Discuss why engineers often prefer to quote tyre specifications in gauge pressure rather than absolute pressure.