Where does a 1 solar-mass protostar appear on an H-R diagram?
A) It is to the right of the main sequence and higher up than the Sun.
B) It is to the right of the main sequence and lower down than the Sun.
C) It is to the left of the main sequence and higher up than the Sun.
D) Nowhere; only stars that have fusion in their cores can be shown on H-R diagrams.
A) It is to the right of the main sequence and higher up than the Sun.
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A disk (radius = 8.0 cm) that rotates about a fixed axis starts from rest and accelerates at a constant rate to an angular velocity of 4.0 rad/s in 2.0 s. What is the magnitude of the total linear acceleration of a point on the rim of the disk at the instant when the angular velocity of the disk is 1.5 rad/s?
A. 24 cm/s2 B. 16 cm/s2 C. 18 cm/s2 D. 34 cm/s2 E. 44 cm/s2
According to our best present predictions about the medical consequences of the Chernobyl nuclear power plant accident, the longer-term cancer deaths caused by that accident will
A) be medically indistinguishable from cancer deaths produced by other causes. B) be very difficult, or impossible, to detect statistically among the large number of other cancer deaths. C) be much more numerous than the roughly 40 deaths caused directly by short-term radiation effects. D) All of the above. E) None of the above.
A magnet will become weaker if it is
A) dropped on a hard surface. B) held in a hot flame. C) either D) neither
Comets are composed of ______________
a. dust and ice b. rock c. helium d. lead e. iron