Which of the following is not an observed characteristic of the cosmic microwave background?
A) It contains prominent spectral lines of hydrogen, the primary chemical ingredient of the universe.
B) It has a perfect thermal radiation spectrum.
C) Its temperature is a little less than 3 Kelvin (3 degrees above absolute zero).
D) Its temperature is the same everywhere, except for small variations at the level of 1 part in 100,000.
A
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A region in the Universe where there are almost no galaxies is called a ________.
A. void B. supermassive black hole C. dark nebula D. zone of avoidance
An 800-N billboard worker stands on a 4.0-m scaffold supported by vertical ropes at each end. If the scaffold weighs 500 N and the worker stands 1.0 m from one end, what is the tension in the rope farthest from the worker?
a. 450 N c. 800 N b. 500 N d. 850 N
An inductor, battery, resistor, ammeter, and switch are connected in series. If the switch, initially open, is now closed, what is the current's final value?
a. zero b. battery voltage divided by resistance c. battery voltage times inductance d. battery voltage divided by inductance
How do we calculate centripetal acceleration?
a. By calculating the acceleration at several points around the circle and averaging. b. By subtracting two velocity vectors separated by a short time interval. c. By adding two velocity vectors separated by a short time interval. d. By calculating the change in speed. e. By calculating the acceleration at several points around the circle and finding the sum.