The "pulse" from a pulsar is due to the rapidly expanding and contracting outer shell of the star
Indicate whether the statement is true or false
FALSE
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Calculate: (a) time elapsed in cooling the surface of the sphere to 204°C and (b) time elapsed in cooling the center of the sphere to 204°C.
A steel sphere with a diameter of 7.6 cm is to be hardened by first heating it to a uniform
temperature of 870°C and then quenching it in a large bath of water at a temperature of 38°C.
The following data apply
GIVEN
FIND
(a) Time elapsed in cooling the surface of the sphere to 204°C
(b) Time elapsed in cooling the center of the sphere to 204°C
ASSUMPTIONS
Constant water bath temperature, thermal properties, and transfer coefficient
SKETCH
In an analysis relating Bohr's theory to the de Broglie wavelength of electrons, when an electron moves from the n = 1 level to the n = 2 level, the circumference for its orbit becomes 4 times greater. This occurs because
a. there are four times as many wavelengths in the new orbit. b. the wavelength of the electron becomes four times as long. c. there are twice as many wavelengths, and each wavelength is twice as long. d. the electron is moving four times as fast.
A 40.0-g block of ice at -15.00°C is dropped into a calorimeter (of negligible heat capacity) containing water at 15.00°C. When equilibrium is reached, the final temperature is 8.00°C
How much water did the calorimeter contain initially? The specific heat of ice is 2090 J/kg ? K, that of water is 4186 J/kg ? K, and the latent heat of fusion of water is 33.5 × 104 J/kg. A) 302 g B) 345 g C) 405 g D) 546 g E) 634 g
When it comes near a heavy nucleus, a gamma ray, which is a high energy photon, can "disappear," and in its place there will be produced an electron and a positron, which both have mass. This pair production is an example of
a. time dilation b. length contraction c. the equivalence of mass and energy d. the principle of relativity e. none of the above