An astronomer examining a compact object could conclude that it was a black hole if it _____
a. emits regular pulses of radiation
b. has a defined event horizon that emits X-rays
c. has an accretion disk
d. has a mass greater than 1.4 solar masses
e. has a mass greater than 3 solar masses
e
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A long copper cylinder 0.6-m in diameter and initially at a uniform temperature of 38°C is placed in a water bath at 93°C. Assuming that the heat transfer coefficient between the copper and the water is 1248 W/(m2 K), calculate the time required to heat the center of the cylinder to 66°C. As a first approximation, neglect the temperature gradient within the cylinder, then repeat your calculation without this simplifying assumption and compare your results.
GIVEN
• A long copper cylinder is placed in a water bath
• Diameter of cylinder (D) = 0.6 m
• Initial temperature (To) = 38°C
• Water bath temperature (T?) = 93°C
• The heat transfer coefficient ( ) ch = 1248 W/(m2 K)
FIND
Calculate the time required to heat the center of the cylinder to 66°C assuming
(a) Negligible temperature gradient within the cylinder
(b) Without this simplification, then
(c) Compare your results
ASSUMPTIONS
• Neglect end effects
• Radial conduction only
SKETCH
The Moon orbits the Earth the Earth orbits the Sun. If the Earth-moon system is ˜1 AU from the Sun and takes ˜1 Earth year to orbit, what is the combined mass of the triple system? Express your answer in solar mass units
a. 1 b. 1.1 c. 1.2 d. 1.3
Rockets that launch satellites into orbit need less thrust when fired from
A) Cape Canaveral in Florida. B) Edwards Air Force Base in California. C) Hawaii. D) location does not affect the required rocket thrust.
What happens to the total relativistic energy of a speedy proton when its relativistic mass doubles?
A) It doubles. B) It more than doubles. C) It less than doubles. D) It must increase, but it is impossible to say by how much.