Why does iron formation cause a high mass star to "have a heart attack"?
What will be an ideal response?
Iron is the most tightly bonded of all nuclei. Fusion reactions leading to its production release radiation pressure to resist gravity, but all heavier nuclei beyond iron will absorb energy in their formation, so without the radiation to keep it inflated, the core collapses rapidly.
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Two solenoids are each made of 2000 turns of copper wire per meter. Solenoid I is 2 m long, while solenoid II is 1 m long. When equal currents are present in the two solenoids, the ratio of the magnetic field BI along the axis of solenoid I to the magnetic field BII along the axis of solenoid II, BI/BII, is
a. 1/4. b. 1/2. c. 1. d. 2 e. 4.
If we went back in time 10 billion years, would we expect Hubble's constant to be identical to the present-day Hubble constant?
A) Yes, a constant never changes. B) No, Hubble's constant is roughly equal to 1 divided by the age of the universe, and 10 billion is a substantial enough number to notice a difference. C) If we went back further in time, it would be different, but 10 billion years is not enough. D) It would only change if we went 10 billion years into the future.
Power: A kilowatt-hour is equivalent to
A. 1000 W. B. 3600 J. C. 3,600,000 J/s. D. 3,600,000 J. E. 3600 J/s
When charges qa, qb, and qc are placed respectively at the corners a, b, and c of a right triangle, the potential at the midpoint of the hypotenuse is 20 V. When the charge qa is removed, the potential at the midpoint becomes 15 V. When, instead, the charge qb is removed (qa and qc both in place), the potential at the midpoint becomes 13 V. What is the potential at the midpoint if both charges qa
and qc are removed? a. 13 V c. 5 V b. 7 V d. 8 V