What prevents a brown dwarf from undergoing nuclear fusion?
A) Degeneracy pressure halts the contraction of a protostar so the core never becomes hot or dense enough for nuclear fusion.
B) There is not enough mass to maintain nuclear reactions in a self-sustaining way.
C) The surface temperature never rises high enough for the radiation to be trapped and heat their interior to the temperatures required for nuclear fusion.
D) Radiation pressure halts the contraction of a protostar so the core never becomes hot or dense enough for nuclear fusion.
E) There are too many heavy elements and not enough hydrogen for fusion to occur in a self-sustaining way.
A
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Modern mammals are descendants of
A) birds that were able to survive the impact that wiped out the dinosaurs 65 million years ago B) sea animals that colonized the land after the impact that wiped out the dinosaurs 65 million years ago C) early mammals that lived under the ground that were able to survive the impact that helped to wipe out the dinosaurs 65 million years ago D) early mammals that killed off the dinosaurs
If the displacement of an object, x, is related to velocity, v, according to the relation x = Av, the constant, A, has the dimension of which of the following?
a. volume c. time b. length d. area
A long solenoid has a radius of 4.0 cm and has 800 turns/m. If the current in the solenoid is increasing at the rate of 3.0 A/s, what is the magnitude of the induced electric field at a point 2.2 cm from the axis of the solenoid?
a. 3.3 × 10^-5 V/m b. 3.6 × 10^-5 V/m c. 3.9 × 10^-5 V/m d. 4.2 × 10^-5 V/m e. 6.0 × 10^-5 V/m
The radioactivity from your body
A. does not cause cancer because it is natural B. is responsible for more than half of the cancer in humans C. does cause cancer, but at a very low rate D. helps reduce natural cancer, just as radiation therapy does