Quimica organica

Chapter 13 Fluids
Conceptual Problems
1 • Determine the Concept The absolute pressure is related to the gauge pressure according to P = Pgauge + Pat. While doubling the gauge pressure will increase the absolute pressure, we do not have enough information to say what the resulting absolute pressure will be.

e is correct.
*2 •

Determine the Concept No. In an environment where g eff buoyantforce; there is no up or down.

Fg

m

v2 r

0 , there is no

•• 3 Determine the Concept As you lower the rock into the water, the upward force you exert on the rock plus the upward buoyant force on the rock balance its weight. When the thread breaks, there will be an additional downward force on the scale equal to the buoyant force on the rock (the water exerts the upward buoyant forceon the rock and the reaction force is the force the rock exerts on the water … and hence on the scale). Let represent the density of the water, V the volume of the rock, and wf the weight of the displaced water. Then the density of the rock is 3 . We can use Archimedes’ principle to find the additional force on the scale. Apply Archimedes’ principle to the rock: Because Vf = Vrock:

B

wfmf g

f

Vf g
1 3

B

M
rock

g

M g 3

Mg

and ( d ) is correct. •• 4 Determine the Concept The density of water increases with depth and the buoyant force on the rock equals the weight of the displaced water. Because the weight of the displaced water depends on the density of the water, it follows that the buoyant force on the rock increases as it sinks. (b) is correct. •• 5Determine the Concept Nothing. The fish is in neutral buoyancy (that is, its density equals that water), so the upward acceleration of the fish is balanced by the downward

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acceleration of the displaced water. •• *6 Determine the Concept Yes. Because the volumes of the two objects are equal, the downward force on each side is reduced by the same amount when they aresubmerged, not in proportion to their masses. That is, if m1L1 = m2L2 and L1 L2, then (m1 c)L1 (m2 c)L2. •• 7 Determine the Concept The buoyant forces acting on these submerged objects are equal to the weight of the water each displaces. The weight of the displaced water, in turn, is directly proportional to the volume of the submerged object. Because Pb > Cu, the volume of the copper must begreater than that of the lead and, hence, the buoyant force on the copper is greater than that on the lead. (b) is correct. 8 •• Determine the Concept The buoyant forces acting on these submerged objects are equal to the weight of the water each displaces. The weight of the displaced water, in turn, is directly proportional to the volume of the submerged object. Because their volumes are the same, thebuoyant forces on them must be the same. (c) is correct. • 9 Determine the Concept It blows over the ball, reducing the pressure above the ball to below atmospheric pressure. • 10 Determine the Concept From the equation of continuity (IV = Av = constant), we can conclude that, as the pipe narrows, the velocity of the fluid must increase. Using Bernoulli’s equation for constant elevation ( P 1 v 2constant ), we can conclude 2 that as the velocity of the fluid increases, the pressure must decrease. (b) is correct. *11 • Determine the Concept False. The buoyant force on a submerged object depends on the weight of the displaced fluid which, in turn, depends on the volume of the displaced fluid. 12 • Determine the Concept When the bottle is squeezed, the force is transmitted equally through thefluid, leading to a pressure increase on the air bubble in the diver. The air bubble shrinks, and the loss in buoyancy is enough to sink the diver.

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13 • Determine the Concept The buoyant force acting on the ice cubes equals the weight of the water they displace, i.e., B wf f Vf g . When the ice melts the volume of water displaced by the ice cubes will occupy the space...