Why do we call dark matter "dark"?
A) It emits no radiation that we have been able to detect.
B) It is dark brown or dark red in color.
C) It blocks out the light of stars in a galaxy.
D) It contains large amounts of dark-colored dust.
A) It emits no radiation that we have been able to detect.
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Water can be brought to a boil by
A) supplying thermal energy. B) reducing air pressure on its surface. C) both of these D) neither of these
A person's hyperopic (farsighted) eye can focus on objects that are 75 cm away and farther. What power and what focal length contact lenses should be prescribed so this person can see objects 25 cm and farther from the eye?
What will be an ideal response?
The walls of an ice chest are made of 2.00-mm-thick insulation having a thermal conductivity 0.00300 W/m?K. The total surface area of the ice chest is 1.20 m2
If 4.00 kg of ice at 0.00°C are placed in the chest and the temperature of the outside surface of the chest is 20.0°C, how long does it take the ice to melt under steady state conditions? The latent heat of fusion of water is 79.6 cal/g = 334 kJ/kg. A) 4.22 h B) 22.1 h C) 17.6 h D) 1.33 d E) 10.3 h
Which of the following features of the Solar System does the solar nebula hypothesis explain?
A. All the planets' orbits lie in nearly the same plane. B. All the planets orbit the Sun in the same direction. C. The planets nearest the Sun contain only small amounts of substances that condense at low temperatures. D. All of these choices are correct.