Compared to young stars, very old stars have
A) exactly the same chemical composition
B) a lower proportion of elements heavier than helium
C) a higher proportion of elements heavier than helium
D) no elements heavier than helium at all
B
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Why is a dense cloud more likely to produce an elliptical galaxy than a spiral galaxy?
A) The higher density of gas has a stronger force of gravity, and therefore the cloud collapses more quickly. B) The thickness of the dense cloud prevents a disk from forming. C) The higher gas density forms stars more efficiently, so all the gas is converted into stars before a disk can form. D) The force of gravity can pull the material into a more spherical shape. E) The more frequent collisions between particles randomize the particle orbits.
When a warm air mass advances over a cold
surface region, it is referred to as a) a stationary front. b) an anticyclone. c) a cold front occlusion. d) simply a warm front.
No one can hear you scream (or fire a weapon) in space, regardless of the Hollywood special effects. Explain why
What will be an ideal response?
An ac power generator produces 50 A (rms) at 3600 V. The voltage is stepped up to 100000 V by an ideal transformer and the energy is transmitted through a long distance power line which has a resistance of 100 ohms. What percentage of the power delivered by the generator is dissipated as heat in the long-distance power line?