(a) What happens to the pressure difference between the top and bottom of the brick in Figure 18.9a when the brick is held deeper in the water?

(b) What happens to the pressure difference when the pressure at the surface of the water is increased?

(c) What is the effect of the pressure in the water on the vertical sides of the brick? 

(d) Consider the same brick held in the air. Does the air exert a buoyant force on the brick? If so, in which direction is this force?

Figure 18.9 Cause of the buoyant force experienced by objects that are partly or fully submerged in a fluid. (a) Brick held under water (b) Free-body diagram that separates force exerted by water on brick's top and bottom surfaces (c) Free-body diagram showing buoyant force exerted by water on brick Fib F brick F F wb wt ... force exerted by water on bottom surface smaller force exerted by water on top surface Fib wb Fb