The Sun is at one focus of the elliptical orbit of the Earth aroundthe Sun. What is atthe other focus?
a) Nothing.
b) The Earth.
c) Mars.
d) The Moon.
e) Jupiter.
Ans: a) Nothing.
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The terrestrial planet with the most effective greenhouse effect is ____________________
Fill in the blank(s) with correct word
The red coloration seen on the Martian surface originates from
A. when Mars' had flowing water, it also has red algae, which stained the surface rocks. B. the iron minerals in the surface rocks combining with oxygen in the atmosphere causing the surface to rust. C. the atmosphere blocking out blue light, only allowing red light to reflect off the surface. D. past volcanic activity covering the surface of the planet with red lava.
Consider a heat treatment process in which steel rods with a 10 cm diameter at an initial temperature of 600°C are inserted into an oil bath at 25°C. Assuming a convection coefficient of 400 W/(m2 K) between the oil and the rod, estimate how long it takes for the centerline of the rod to cool to 60°C. If the steel rod, which is 1 m long, is withdrawn from the bath at this point in the process, i.e., when the centerline temperature has reached 60°C, estimate the rate at which heat must be extracted from the oil to maintain its temperature constant during the process of treating 25 rods per hour.
GIVEN
• Heat treatment of steel rod inserted in oil bath
• Rod outside diameter = 0.1 m
• Initial temperature (T0) = 600°C
• Oil bath temperature (T?) = 25°C
• The average heat transfer coefficient ch = 400 W/(m2 K)
FIND
• Time it takes for centerline of the rod to cool to 600C.
• Rate at which heat must be extracted from oil to maintain its temperature constant during the process of treating 25 rods per hour.
ASSUMPTIONS
• Radial conduction only in billet
• Uniform and constant properties
SKETCH
On an axis in which moving from right to left is positive, what is the displacement and distance of a student who walks 32 m to the right and then 17 m to the left?
a. Displacement is -15 m and distance is -49 m. b. Displacement is -15 m and distance is 49 m. c. Displacement is 15 m and distance is -49 m. d. Displacement is 15 m and distance is 49 m