Describe two methods that could be used to determine the temperature of a star
What will be an ideal response?
The Balmer thermometer is a method of determining the temperature of a star. It works because the strength of the Balmer lines depends on the temperature of the star's surface layers. Theoretical calculations can predict how strong the Balmer lines should be for stars of various temperatures. Temperature has a similar effect on the spectral lines of other elements, but the temperature at which the lines reach their maximum strength is different for each element. Another way is to use the temperature-luminosity relationship.
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Work-Energy Theorem: Three cars (car L, car M, and car N) are moving with the same speed and slam on their brakes. The most massive car is car L, and the least massive is car N. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, for which car is the amount of work done by friction in stopping it the greatest?
A. The amount of work done by friction is the same for all cars. B. Car L C. Car M D. Car N
A 50-gram sample of dry ice (solid CO2) is placed in a 4-liter container. The system is sealed and allowed to reach room temperature (20°C). By approximately how much does the pressure inside the container increase when the dry ice turns to gas? (Ignore the initial volume of the sample.)
The demonstration in this figure is often shown as a magician's trick. What in fact is the "trick?"
a. When the magician yanks the tablecloth rapidly, the inertia of the dishes prevents them from accelerating significantly during the short time the force of friction from the moving tablecloth acts. b. The magician uses magnets or some other external device to keep the dishware in place. c. The tablecloth has almost zero mass, or inertia. Hence, it is easy to pull away from the dishware. d. The mass of the tablecloth prevents it from accelerating rapidly enough to exert much force on the dishes. e. The dishes have much less inertia than the tablecloth.
The Ga-As phase diagram has a compound GaAs (?-phase) that is a single vertical line at 50 atomic % As. Can ?-phase be produced that has 55 atomic % As? _____________
Fill in the blank(s) with the appropriate word(s).