In the evolution of massive stars, what is the significance of the temperature 600 million K?
A) It is the temperature at which helium fuses into carbon.
B) It is the temperature needed for carbon fusing into heavier elements.
C) It is the main sequence core temperature which makes massive stars so bright.
D) It is the temperature needed for helium burning into boron.
E) It is the final temperature reached during their evolution.
B
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At extremely high temperatures (e.g., millions of degrees), which of the following best describes the phase of matter?
A) a gas of rapidly moving molecules B) a plasma consisting of positively charged ions and free electrons C) a gas consisting of individual, neutral atoms, but no molecules D) a plasma consisting of rapidly moving, neutral atoms E) matter cannot exist at extremely high temperatures.
A 6.0 kg box slides down an inclined plane that makes an angle of 39° with the horizontal. If the coefficient of kinetic friction is 0.40, at what rate does the box accelerate down the slope?
A) 3.1 m/s2 B) 3.4 m/s2 C) 3.7 m/s2 D) 4.1 m/s2
Greenhouse gasses include
a. water vapor. b. CO2. c. CO. d. methane.
A block of mass 5.00 kg rests on a horizontal surface where the coefficient of kinetic friction between the two is 0.200 . A string attached to the block is pulled horizontally, resulting in a 3.00 m/s2 acceleration by the block. Find the tension in the string. (g = 9.80 m/s2)
a. 0.200 N c. 19.8 N b. 9.80 N d. 24.8 N