P25

          P = 5 atm,     1 atm = 10**5 Pa (N/m**2)

          F= 5x10**5 Pa = 50 N/cm**2

P39

          h = 61 cm,           P = rgh + 1 atm = 10**3 x 9.8 x 0.61 Pa + 10**5 Pa = 1.06 x10**5 Pa

P40

          P = F/A + rgh = 10**3 N/0.1 m**2 + 13.6 x 10**3 x 9.8 x 0.1

            = 10**4  Pa + 13.3 x 10**3  Pa = 1.4 x 10**4  Pa

P47

          F = Pav A,     Pb(at bottom) = rgh = 10**3 x 9.8 x 3 = 29.4 x 10**3 N/m**2

          Pav = Pb /2 = 14.7 x 10**3 Pa    

          F = Pav A = 14.7 x 10**3  N/m**2 x 15 m**2 = 2.2 x 10**5  N

P71 (Chapter 12)

        PV = NkBT,     

        N = PV / kBT = 0.1 x 10**6 x 5 x 10**-4 / (1.38 x 10**-23 x 293 K)

            = 1.2 x 10**22 molecules