(a) people/km^2
(b) people/km^2
(c) people/km^2
(d) people/km^2
2.2 The density of air at standard atmospheric pressure and 15°C is 1.23 kg/m^3. (a) What is the total mass of the air in a
rectangular room that measures 5.25 m × 4.20 m × 2.15 m? (b) What is the weight of the air in the room? (c) What is the
weight of the air in the Pentagon office building in Washington, DC, which has a volume of 2.2×10^6 m^3?
(a) kg
(b) N
(c) N
2.3 If you have ever toured a facility (such as a cyclotron laboratory) where people have to be protected against radiation, there
may have been lead bricks lying around, and you may have been given the opportunity to heft one. It is a surprising
experience. The dimensions of a standard brick are 9.2 cm × 5.7 cm × 20 cm, and the density of lead is 11,300 kg/m^3. (a)
What is the mass of a (standard) lead brick? (b) What is the weight of the brick, in pounds?
(a) kg
(b) lb
2.4 In the opening sequence of the movie, Raiders of the Lost Ark, the intrepid explorer Indiana Jones deftly swipes a golden idol
from a Mayan temple, instantly replacing it with a bag of sand of the same size to neutralize the ancient weight-based booby
trap protecting it. (a) The density of gold is 19,300 kg/m3. If the idol's mass is 11.3 kg and it is solid gold, calculate its volume.
(b) The density of silica sand is 1220 kg/m^3. What is the mass of a sandbag of equal volume? (c) Is the scene realistic?
(a) m^3
(b) kg
(c) Yes NoSection 3 - Pressure
3.1 (a) A fashionable spike heel has an area of 0.878 cm^2. When a 61.4 kg woman walking in this shoe sets her full weight down
on the heel, what is the pressure it exerts on the floor? (b) The heel of a "sensible" shoe has an area of 38.3 cm^2. When the
same woman sets her weight on this heel, what is the pressure?
(a) Pa
(b) Pa
3.2 During the first half of the twentieth century, research into the behavior of materials at ultrahigh pressures was conducted
using huge hydraulic presses. In 1958 scientists had a sudden insight: instead of building ever larger presses to exert ever
larger forces on material samples of a given area, why not use relatively modest forces and an extremely small area? They
invented the diamond anvil pressure cell. This device incorporates two opposed diamonds (the "anvils") whose sharp pointshave been slightly filed off to produce roughly circular flat surfaces with a diameter of 250 μm. A minute sample of material is
placed between these surfaces and the diamonds are pressed together using leverage. (a) If the diamonds are 2.15 cm from
the pivot point of the lever and a scientist bears down with a force of 255 N at a distance of 14.2 cm from the pivot point, what
force presses the diamonds together? (b) What is the pressure exerted on the sample?
(a) N
(b) Pa
3.3 A 106 kg man is traveling through the snow. He finds that when he wears only his boots, the sole of each of which has an
area of 136 cm^2 , he sinks into the snow up to his calves. Figuring that he will never get to Grandma's house this way, he dons
his snowshoes, made of a lightweight flat material with no holes. Each snowshoe can be modeled as a rectangle, 37.0 cm
wide and 115 cm long, with a half-circle added to the front and the back as a "toe" and a "heel." (a) What pressure does the
man exert on the frozen crust of the snow when he puts his entire weight on one booted foot? (b) What pressure does the
man exert when he puts his weight on one snowshoe?
(a) Pa
(b) Pa
3.4 An automobile has four tires, each one inflated to a gauge pressure of 24.0 psi, or 1.66×10^5 Pa. Each tire is slightly flattened
by its contact with the ground, so that the area of contact is 17.5 cm by 12.0 cm. What is the weight of the automobile?
N
3.5 An advertisement for a certain portable vacuum cleaner shows off its power with a photograph of the vacuum-cleaner wand
suspending a bowling ball by the strength of its suction. The vacuum cleaner can maintain a moderate vacuum inside the
apparatus at an absolute pressure of 3.53×10^4 Pa (against an outside atmospheric pressure of 1.01×10^5 Pa) when the intake
wand is closed. The wand is a hollow metal cylinder with an inside diameter of 3.19 cm. What is the weight of the heaviest ball(^270) Copyright 2007 Kinetic Books Co. Chapter 13 Problems