At absolute zero, a substance has
A) absolutely no molecular motion.
B) no more energy to give up.
C) no volume.
D) all of the above
Answer: B
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Three particles are placed in the xy plane. A 40-g particle is located at (3, 4) m, and a 50-g particle is positioned at (?2, ?6) m. Where must a 20-g particle be placed so that the center of mass of this three-particle system is located at the origin?
a. (?1, ?3) m b. (?1, 2) m c. (?1, 12) m d. (?1, 7) m e. (?1, 3) m
Atomic Nucleus: All nuclei of a given element have the same number of
A. neutrons. B. protons. C. nucleons. D. protons + neutrons.
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. including a contact resistance of 0.1 K/W at each of the interfaces.
GIVEN
• 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
• Contact resistance at each interface (Ri) = 0.1 K/W FIND
(a) Rate of heat transfer through the wall (q) (b) Temperatures at the interfaces
ASSUMPTIONS
• One dimensional conduction
• The system is in steady state
SKETCH
Electrons exist in a cloud-like structure around the nucleus called a(n) ________.
A. spectrum B. orbital C. particle wave D. level