1-(a) A copper pipe, used for plumbing from the water main to a house, is 3 mete
ID: 1919998 • Letter: 1
Question
1-(a) A copper pipe, used for plumbing from the water main to a house, is 3 meters long and has a circular cross-section 2.8 cm in diameter. There is a 2 cm diameter hole in the center of the cross-section for the entire length of the rod. What is the volume of copper in the rod in cubic inches?
(b) The density of copper is
559 lbm/ft3. What is the mass of the copper pipe in pounds?
2- (a) A probe sent to the surface of Mars uncovers a pure platinum disc inscribed with the message, "We'll be right back" (in Martian, of course!). The disc is
4 inches thick and 0.6 meters in diameter. The density of platinum is 21,450 kg/m3. What is the mass of the platinum disc in pounds (lbm)?
(b) The Martian acceleration due to gravity is 3.61
m/s2 while Earth's gravitational constant is 32.2 ft/s2. What is the Earth weight of the disc in Newtons?
Explanation / Answer
(1)Volume of the pipe = (length) x (cross sectional area of material)
= 3 x [ pi x (2.8/2/100)^2 - pi x (2/2/100^2) ] cubic meters --------(note-conversion of cm to m)
= 3 x pi x (2.8^2 - 2^2)/40000 cubic meters
= x pi x (2.8^2 - 2^2)/40000 x (39.37)^3 cubic inches
=107.3579 cubic inches
Mass of the pipe = 559 x 107.3579 /(12^3) = 34.72978 = 34.73 pounds
(2)Convert all units to SI.
Disc: 0.0508m thick, 0.6m diameter
volume of disc = 0.0508 * (pi)0.3^2 = 0.0255 cubic meters
mass of disc = 0.0255 m3 * 21450 kg/m3 = 547.72 kg
mass of disc in pounds = 547.72 kg * 2.205 lb/kg = 1207.5 lb
The second question is a bit confusing, not quite clear why Martian gravitational constant is needed.
Earth's gravitational constant: 9.81 m/s2
force exerted by disc = 9.81 m/s2 * 547.72 kg = 5375 N
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