Consider the sun and its largest planet Jupiter. On the line joining them, how far from the center of the sun is their center mass? Is it within or outside the sun? (Jupiter-sun distance is 778 × 106 km, diameter of the sun is 1
4 × 106 km, the sun is 1000 times as massive as Jupiter)
0.78 × 106 km from the center of the sun, just outside the solar surface
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In our location in the Milky Way, the galactic disk is only about ________ ly thick
A) 10 B) 100 C) 1,000 D) 10,000 E) 100,000
On the planet Jupiter, a dropped object picks up a speed of 20 m/sec in one second. How fast will it be going at the end of 3 seconds of fall, neglecting "air" resistance on Jupiter?
A) 40 m/sec B) 80 m/sec C) 60 m/sec D) 180 m/sec E) 20 m/sec
A section of a composite wall with the dimensions shown below has uniform temperatures of 200°C and 50°C over the left and right surfaces, respectively. If the thermal conductivities of the wall materials are: kA = 70 W/(m K), kB = 60 W/(m K), kc = 40 W/(m K) and kD = 20 W/(m K), determine the rate of heat transfer through this section of the wall and the temperatures at the interfaces.
GIVEN
• A section of a composite wall
• Thermal conductivities
? kA = 70 W/(m K)
? kB = 60 W/(m K)
? kC = 40 W/(m K)
? kD = 20 W/(m K)
• Surface temperatures
? Left side (TAs) = 200°C
? Right side (TDs) = 50°C
FIND
(a) Rate of heat transfer through the wall (q) (b) Temperature at the interfaces
ASSUMPTIONS
• One dimensional conduction
• The system is in steady state
• The contact resistances between the materials is negligible
SKETCH
What is the first law of thermodynamics?
a. The increase in the internal energy of a system is equal to the heat added plus the work done on the system. b. Heating a system makes it more disordered. c. The increase in the internal energy of a system is equal to the heat added times the work done on the system. d. The increase in the internal energy of a system is equal to the work done on the system. e. Objects in motion tend to remain in motion; objects at rest tend to remain at rest.