Calculate the energy En, in electron volts, of a hydrogen atom's electron with n = 5
-0.544 eV
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A 3.10-eV electron is incident on a 0.40-nm barrier that is 5.67 eV high
What is the probability that this electron will tunnel through the barrier? (1 eV = 1.60 × 10-19 J, mel = 9.11 × 10-31 kg, h = 1.055 × 10-34 J ? s, h = 6.626 × 10-34 J ? s) A) 1.4 × 10-3 B) 9.0 × 10-4 C) 1.0 × 10-3 D) 1.5 × 10-3 E) 1.2 × 10-3
If you were in a spaceship traveling at a speed close to the speed of light (with respect to earth) you would notice that
A) some of your physical dimensions were smaller than normal. B) your mass is different than normal. C) your pulse rate is different than normal. D) None of these effects occur. E) More than one of these effects occur.
At which latitude is the noonday Sun overhead twice a year?
a. 30°S b. 23°S c. 24°N d. 30°N
A copper sphere initially at a uniform temperature of 132°C is suddenly released at the bottom of a large bath of bismuth at 500°C. The sphere diameter is 1 cm and it rises through the bath at 1 m/s. How far will the sphere rise before its center temperature is 300°C? What is its surface temperature at that point? (The sphere has a thin nickel plating to protect the copper from the bismuth.)
GIVEN
• A copper sphere with a thin nickel plating rising through a bath of bismuth
• Initial copper temperature (To) = 132°C (uniform)
• Bismuth temperature (T?) = 500°C
• Ascent velocity (U?) = 1 m/s
• Sphere diameter (D) = 1 cm = 0.01 m
FIND
(a) Distance sphere will rise before its center temperature, T(o,t) = 300°C (b) The sphere surface temperature at that time, T(ro,t) ASSUMPTIONS
• Thermal resistance of the nickel plating is negligible
• Thermal properties of the copper can be considered uniform and constant
SKETCH
