Explain why it is difficult to see Mercury in the night sky
What will be an ideal response?
Mercury stays near the ecliptic because it has an orbit inside Earth's orbit. To find Mercury, you need to look above the western horizon just after sunset or above the eastern horizon just before sunrise. However, Mercury is hard to see against the glare of the sky near the Sun, and also it is often hidden in the clouds and haze near the horizon.
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Helium flash occurs
a. because helium is very explosive and cannot be controlled when the nuclear reactions occur. b. because degenerate gas does not allow the core to expand as it heats up. c. in Cepheid variables. d. in stars with masses less than 0.4 M. e. None of the other choices are correct.
An external interaction exerts a force 
on a certain system as the place where the force is applied moves a displacement 
. Which of the following is the correct component expression for the work done by the interaction on the system?
A. W = [Fx dx, Fy dy, Fz dz] B. W = ?[Fx dx, Fy dy, Fz dz]? C. W = Fx dx + Fy dy + Fz dz D. Some other expression (specify)
The superposition principle has to do with which of the following?
a. effects of waves at great distances b. the ability of some waves to move very far c. how displacements of interacting waves add together d. relativistic wave behavior
One kilogram of chilled water at 32°F (0°C) is placed in a freezer which is kept at 0°F (?18°C). Approximately how much electric energy (in kilocalories) is needed to operate the compressor to cool this water to 0°F if the room temperature is maintained at 75°F (24°C)? (LF,ice = 3.33 × 10^5 J/kg; cice = 2.09 × 10^3 J/kg/°C)
a. 13 b. 1.5 c. 15 d. 16 e. 33