Physics 114 – Lecture 29 §10.4 Atmospheric Pressure and Gauge Pressure Atmospheric pressure, PA, is, on average, at sea level, PA = 1.013 X 105 N/m2 Other units are used, for example, 1 bar = 1.00 X 105 N/m2, see Table 10.2, p 261 in Giancoli Study Example 10.4: finger holding water in a straw Gauge Pressure Pressure above atmospheric pressure, e.g., pressure measured by a tire gauge and many other gauges P = PA + PG L29-s1,7

Physics 114 – Lecture 29 §10.5 Pascal’s Principle Pascal’s Principle states that if an external pressure is applied to a confined fluid the pressure at all points within the fluid is increased by the amount of the external pressure. E.g., hydraulic jack L29-s2,7

Physics 114 – Lecture 29 §10.6 Measurement of Pressure; Gauges and the Barometer Open tube manometer L29-s3,7

Physics 114 – Lecture 29 Aneroid gauge L29-s4,7

Physics 114 – Lecture 29 Tire gauge L29-s5,7

Physics 114 – Lecture 29 Atmospheric pressure is conveniently measured with a barometer, usually a mercury barometer P = ρgh = (13.6 X 103 kg/m3) X 9.80 m/s2 X 0.760 m = 1.013 X 105 N/m2 = 1.00 atm • This is often stated as: PA = 0.760 m of Hg (mercury) = 76.0 cm of Hg = 760 mm of Hg • Study Example 10.5 - suction L29-s6,7

Physics 114 – Lecture 29 §10.7 Buoyancy and Archimedes’ Principle FB = F2 – F1 = ρgAh2 – ρgAh1 = ρgA Δh = ρgV = mg (mass of fluid displaced) •Study Examples 10.6, 10.7, 10.8, 10.9, 10.10 L29-s7,7