When a star's inward gravity and outward pressure are balanced, the star is said to be:
A) in gravitational collapse.
B) in thermal expansion.
C) in rotational equilibrium.
D) in hydrostatic equilibrium.
E) a stage 2 protostar.
D
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A 125 g pendulum bob hung on a string of length 35 cm has the same period as when the bob is hung from a spring and caused to oscillate. What is the spring’s elastic constant?
A. 1.9 N/m B. 3.5 N/m C. 5.2 N/m D. 27 N/m
A carnival Ferris wheel has a 15-m radius and completes five turns about its horizontal axis every minute. What is the acceleration of a passenger at his lowest point during the ride?
a. 5.7 m/s2 downward b. 4.1 m/s2 upward c. 14 m/s2 downward d. 4.1 m/s2 downward e. 19 m/s2 downward
Suppose you place an object in front of a concave mirror. Which of the following statements must be true? (There could be more than one correct choice.)
A) The image of the object will always be smaller than the object. B) The image of the object will always be inverted. C) No matter where you place the object, a real image of the object will be formed. D) No matter where you place the object, the image of the object will always be virtual and upright. E) If you position the object between the mirror and the focal point of the mirror, its image must be upright and virtual.
If y = 0.02 sin (30x - 400t) (SI units), the velocity of the wave is
a. 3/40 m/s b. 40/3 m/s c. 60p/400 m/s d. 400/60p m/s e. 400 m/s