The traditional "top-down" hypothesis states that the galaxy formed
a. from a large spherical cloud of gas that was rotating very slowly.
b. from a large cloud of material that broke off a larger galaxy.
c. from material that had been ejected in the violent explosion of a dying galaxy.
d. as a result of mergers between several smaller groups of gas, dust, and stars.
e. as two massive galaxies collided.
a
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When the microwave background radiation was emitted, about how big was the universe?
A) smaller than the head of a pin B) 1/1,000,000 its current size C) 1/100,000 its current size D) 1/1,000 its currents size E) 1/100 its current size
A 30-kg child runs at 3.0 m/s and jumps onto a shopping cart and holds on for dear life. The cart has a mass of 20 kg. Assuming the child rides on the cart after the collision, the speed of the child and shopping cart just after the child jumps on is
A. zero. B. 3.0 m/s. C. 2.5 m/s. D. 1.8 m/s.
A solar cell has a light-gathering area of 10 cm2 and produces 0.2 A at 0.8 V (DC) when illuminated with S = 1000 W/m2 sunlight. What is the efficiency of the solar cell?
a. 16% b. 7% c. 23% d. 4% e. 32%
The term "timbre" refers to which of the following?
a. Any musical instrument made primarily of wood. b. The quality of sound from instruments due to the mixture of harmonics. c. Instruments that have valves. d. An instrument made in France.