Section 5 - Sample problem: pressure at the bottom of a lake
5.1 In the movie Creature from the Black Lagoon, the depth of the freshwater lagoon at its muddy and inscrutable bottom where
the Creature lurks is 15.2 m. (a) What is the gauge pressure at the bottom of the lagoon? (b) What is the absolute pressure at
the bottom of the lagoon? (c) Who played the Creature in this classic 1954 horror film?
(a) Pa
(b) Pa
(c) i. Ben Chapman
ii. Johnny Depp
iii. Groucho Marx
iv. Fay Wray
5.2 Saturn's moon Titan is the largest moon in the solar system. Its mostly-nitrogen atmosphere exerts a pressure of 1.60×10^5 Pa
at the moon's surface (a pressure about 60% greater than Patm at the surface of the Earth). Scientists speculate that it may
have lakes and seas of "gasoline," a mixture of liquid methane and ethane. Suppose that there is a gasoline lagoon on Titan,
43.7 m deep, and consisting of 63.7% methane and 36.3% ethane, which have densities of 465 kg/m^3 and 570 kg/m^3
respectively. (a) Assuming that the acceleration due to gravity on Titan is 1.35 m/s^2 , what is the gauge pressure at the bottom
of the lagoon? (b) What is the absolute pressure at the bottom of the lagoon?
(a) Pa
(b) PaSection 6 - Physics at work: measuring pressure
6.1 The gauge pressure at the bottom of a pint of beer, at a depth of 14.6 cm, is 1450 Pa. (a) What is the density of the beer? (b)
What is the absolute pressure at the bottom of the pint?
(a) kg/m^3
(b) Pa
6.2 (a) Convert 1.05 bar to torr, using the relationships 1 bar = 10^5 Pa and 1 atm = 1.013×10^5 Pa = 760 torr. Express your answer
to the nearest torr. (b) There is a photograph of a dial-type barometer in the textbook, calibrated in both millibars and
millimeters of mercury. On this barometer's scales, 1000 millibars (1 bar) appears to be approximately equal to 750 mm (750
torr) of mercury. Is this approximation good to the nearest torr?
(a) torr
(b) Yes No
6.3 The mercury column of an open tube manometer has a height of 0.0690 m. What is the absolute pressure inside the
manometer vessel?
Pa
6.4 The pressure inside a manometer vessel is 1.42e+5 Pa. How high is the column of mercury in the open tube of the
manometer?
mSection 7 - Archimedes’ principle
7.1 The sizes of ships are commonly expressed in "tons displaced". If a naval vessel displaces 7.67e+3 tons, this means it
displaces that weight of water. What is the volume of the water displaced by this ship? Use the fact that 1 ton is equal to
8.90×10^3 N, and take the density of seawater to be 1030 kg/m^3.
m^3
7.2 A cylindrical metal can with a radius of 4.25 cm is floating upright in water. A rock is placed in the can, causing it to sink
0.0232 m deeper into the water. What is the weight of the rock?
N
7.3 The dry weight of a man is 845 N. When he is submerged underwater, the reading on the scale is only 43.2 N. (a) What is the
volume of the man? (b) What is the density of the man? (c) The density of fat is 209 kg/m^3 , and the density of the "lean" parts
of the human body (muscle, bones, and so on) is 2670 kg/m^3. What percentage of the man's body mass is "lean body mass"?
(a) m^3
(b) kg/m^3
(c) %Section 8 - Sample problem: buoyancy in water
8.1 You are fishing off a bridge. Suddenly you feel a tug on the vertical fishing line. Elated, you begin hauling in your catch at(^272) Copyright 2007 Kinetic Books Co. Chapter 13 Problems