## ABSTRACT

(a) The pressure P equals the mass per unit area of the column of air xg, so the mass M above an area A is 22.1 Columns of air M = P x A = 1.0 X 105 N m- 2 x (2 x 10- 2 m 2) = 1204 kg I, 9 9.81 m S-2 .. where we have taken the area of the head to be 7f(8 cm)2 2 x 10- 2 m 2. (b) The external pressure is balanced by an equal internal pressure.