Spiral and irregular galaxies have active star formation
a. True
b. False
Indicate whether the statement is true or false
True
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Determine the steady-state temperatures of two radiation shields placed in the evacuated space between two infinite planes at temperatures of 555 K and 278 K. The emissivity of all surfaces is 0.8.
GIVEN
-Two radiant shields placed in the evacuated space between two infinite planes
-Temperature of the planes
-T1 = 555 K
-T4 = 278 K
-Emissivity of all surface (?) = 0.8
FIND
-The steady state temperatures of the shields (T2, T3)
ASSUMPTIONS
• All surfaces are gray and diffuse
SKETCH
Consider an AC series circuit containing a coil, capacitor and resistance. Tripling the frequency will change the circuit's impedance by what factor?
a. 1/3 b. 1.0 c. 3 d. Information is insufficient to determine answer.
An example of a diverging spherical mirror is
a. a bathroom mirror. b. a round Christmas tree ornament. c. a flashlight reflector. d. none of these.
A 5.0-kg mass is attached to the ceiling of an elevator by a rope whose mass is negligible. What force does the mass exert on the rope when the elevator has an acceleration of 4.0 m/s2 upward?
a. 69 N downward b. 29 N downward c. 49 N downward d. 20 N downward e. 19 N downward