Chapter 10: Q2P (page 260)
(I) What is the approximate mass of air in a living room 5.6× 3.6× 2.4m?
The mass of the air is 62.4 Kg.
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A 3.2-N force is applied to the plunger of a hypodermic needle. If the diameter of the plunger is 1.3 cm and that of the needle is 0.20 mm, (a) with what force does the fluid leave the needle? (b) What force on the plunger would be needed to push fluid into a vein where the gauge pressure is 75 mm-Hg? Answer for the instant just before the fluid starts to move.
(a) Show that the flow speed measured by a venturi meter (see Fig. 10-29) is given by the relation
\({{\bf{v}}_{\bf{1}}}{\bf{ = }}{{\bf{A}}_{\bf{2}}}\sqrt {\frac{{{\bf{2}}\left( {{{\bf{P}}_{\bf{1}}}{\bf{ - }}{{\bf{P}}_{\bf{2}}}} \right)}}{{{\bf{\rho }}\left( {{\bf{A}}_{\bf{1}}^{\bf{2}}{\bf{ - A}}_{\bf{2}}^{\bf{2}}} \right)}}} \).
(b) A venturi meter is measuring the flow of water; it has a main diameter of \({\bf{3}}{\bf{.5\;cm}}\) tapering down to a throat diameter of \({\bf{1}}{\bf{.0\;cm}}\). If the pressure difference is measured to be \({\bf{18\;mm - Hg}}\), what is the speed of the water entering the venturi throat?
A fire hose exerts a force on the person holding it. This is because the water accelerates as it goes from the hose through the nozzle. How much force is required to hold a \({\bf{7}}{\bf{.0}}\;{\bf{cm}}\)-diameter hose delivering \({\bf{420}}\;{\bf{L/min}}\)through a \({\bf{0}}{\bf{.75}}\;{\bf{cm}}\)-diameter nozzle?
Why does an ocean liner float?
(a) It is made of steel, which floats.
(b) It's very big size changes the way water supports it.
(c) It is held up in the water by large Styrofoam compartments.
(d) The average density of the ocean liner is less than that of seawater.
(e) Remember the Titanic—ocean liners do not float.
(II) The maximum gauge pressure in a hydraulic lift is 17.0 atm. What is the largest-size vehicle (kg) it can lift if the diameter of the output line is 25.5 cm?
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