Why did the solar nebula heat up as it collapsed?
A) As the cloud shrank, its gravitational potential energy was converted to thermal energy.
B) Collisions among planetesimals generated friction and heat.
C) Radiation from other nearby stars that had formed earlier heated the nebula.
D) Nuclear fusion occurring in the core of the protosun produced energy that heated the nebula.
E) The shock wave from a nearby supernova heated the gas.
A
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The lowest temperature possible in nature is
A) 0 degrees C. B) -273 degrees C. C) 4 K. D) none of the above
Why are lunar eclipses more commonly seen than solar eclipses?
A) Lunar eclipses occur at night and are easier to see. B) The Moon goes around the Earth faster than the Earth goes around the Sun. C) The Earth casts a bigger shadow than the Moon. D) The tilt of the Moon's axis is smaller than the Earth's. E) The Moon is much closer to the Earth than the Sun.
Identical masses m are attached to identical springs of spring constant k suspended from the ceiling. With both masses hanging in their equilibrium positions, mass A is pulled down 10 cm and released while mass B is pushed up 10 cm and released. Which statement is correct?
a. Mass A will travel a smaller distance to its highest point than mass B will travel to its lowest point. b. Mass A will travel a greater distance to its highest point than mass B will travel to its lowest point. c. Masses A and B will travel equal distances between their highest and lowest points. d. More work was done on mass A by the extending force than on mass B by the compressing force. e. The total work done on mass A by the extending force was equal to the total work done on mass B by the compressing force.
The number of protons in a nucleus is the __________ number
Fill in the blank(s) with correct word