(a) Calculate the absolute pressure at the bottom of a fresh -water lake at a de
ID: 1293136 • Letter: #
Question
(a) Calculate the absolute pressure at the bottom of a fresh -water lake at a depth of 30.3 m. Assume the density of the water is 1.00 *10^3 kg/m^3 and the air above is at a pressure of 101.3 kPa. Pa (b) What force is exerted by the water on the window of an underwater vehicle at this depth if the window is circular and has a diameter of 33.9 cm? N A sample of an unknown material appears to weigh 265 N in air and 165 N when immersed in alcohol of specific gravity 0.700. (a) What is the volume of the material? m^3 (b) What is the density of the material? kg/m^3 A liquid (p = 1.65 g/cm^3 ) flows through a horizontal pipe of varying cross section as in the figure below. In the first section, the cross-sectional area is 10.0 cm^2 , the flow speed is 292 cm/s, and the pressure is 1.20 x 10^5 Pa. In the second section, the cross-sectional area is 3.50 cm^2. (a) Calculate the smaller section's flow speed. m/s (b) Calculate the smaller section's pressure. PaExplanation / Answer
a) The absolute pressure at bottom of the lake
P = p0 + p g h = (101.3 * 103) + (1 * 103 * 9.8 * 30.3)
= 3.98 * 105 Pa
b) F = P A = P pi r2
= 3.98 * 105 * pi * 0.16952
F = 3.59 * 104 Pa
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2) W = 265 N, W' = 165 N
Density of alcohol = 0.7 * 1000 = 700 kg.m3
Wa = 265 - 165 = 100 N
Volume of a material V = B / p' g = 100 / (700 * 9.8)
= 0.0146 m3
b) density = mass / volume
m = weight in air / g = 265 / 9.8 = 27.04 Kg
p = m / v = 27.04 / 0.0146
= 1855 kg/m3
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