Mercury is more than 60 percent denser than the Moon
a. True
b. False
Indicate whether the statement is true or false
True
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The rest mass of a photon is zero kg
Indicate whether the statement is true or false
From the edge of a roof top you toss a green ball upwards with initial velocity v0 and a blue ball downwards with the same initial velocity. When they reach the ground below,
A) the green ball will be moving faster than the blue ball. B) the blue ball will be moving faster than the green ball. C) the two balls will have the same speed.
A small, hot object makes thermal contact with a more massive, equally hot object. Consequently,
1.there will be a net flow of energy from the smaller object to the larger object. 2.there will be a net flow of energy from the larger object to the smaller object. 3.there will be zero net flow of energy. 4.more information is required to determine the direction of the net flow of energy.
Two coaxial parallel plate discs are situated relative to each other as shown in the sketch. The diameter of the upper plate is 20 cm, and that of the lower plate is 40 cm. The lower plate is maintained at a uniform temperature of 500 K and the upper temperature is maintained at 456 K. To maintain these relative temperatures, a heater has to be installed in the upper plate. Assuming an environmental temperature of the surroundings at 300 K, determine the power necessary of the heater in the upper plate to maintain the two constant plate temperatures under steady state conditions.
GIVEN
• Two coaxial parallel plate discs at distance of L = 20 cm=0.2 m
• Upper plate diameter (D1) = 20 cm = 0.2 m
• Lower plate diameter (D2) = 40 cm = 0.4 m
• Upper plate temperature (T1) = 456 K
• Lower plate temperature (T2) = 500 K
• Surrounding temperature (Tsurr) = 300 K
FIND
(a) Power necessary of the heater in upper plate to maintain the constant plate temperatures under steady state conditions.
SKETCH
PROPERTIES AND CONSTANTS
The Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/(m2 K4)