Main sequence stars have radii ranging from about 0.03 solar radius to 30 solar radius
Indicate whether the statement is true or false
TRUE
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A planet is orbiting a star. Which of the following statements is true for the acceleration and gravitational forces in this situation?
A) The acceleration of the planet is much more than the acceleration of the star, and the gravitational force on the planet is much more than the gravitational force on the star. B) The acceleration of the planet is much more than the acceleration of the star, but the gravitational force on the star is the same but opposite the gravitational force on the planet. C) The gravitational force on the star is much smaller than the gravitational force on the planet, but the accelerations are equal and opposite.
In a single-pass counterflow heat exchanger, 4536 kg/h of water enter at 15°C and cool 9071 kg/h of an oil having a specific heat of 2093 J/(kg K) from 93 to 65°C. If the overall heat transfer coefficient is 284 W/(m2°C), determine the surface area required.
GIVEN
• Oil and water in a single-pass counterflow heat exchanger
• Water flow rate m w= 4536 kg/h = 1.26 kg/s
• Oil flow rate m o= 9071 kg/h = 2.52 kg/s
• Inlet temperatures: Water (Tw,in) = 15°C Oil (To,in) = 93°C
• Oil outlet temperature (To,out) = 65°C
• Oil specific heat (cpo) = 2093 J/(kg °C)
• Overall heat transfer coefficient (U) = 284 W/(m2 °C)
FIND
• The surface area (A) required
ASSUMPTIONS
• Steady state
• Constant thermal properties
SKETCH
PROPERTIES AND CONSTANTS
the specific heat of water at 20°C (cpw) = 4182 J/(kg K)
The stars stay in "fixed" positions on the celestial sphere because they
A) are all located at precisely the same distance from Earth. B) are so far away that our eyes don't notice their motions through space. C) remain stationary relative to our solar system in space. D) were given their names by ancient civilizations.
At a certain instant in time, the electric field of an electromagnetic wave in free space points in the -z direction, and the magnetic field points in the +y direction. In what direction is this wave traveling?
A) +x direction B) -x direction C) +y direction D) -z direction E) +z direction