If the density of the universe is at the critical density, this means that:
A) the universe is expanding at a rate equal to the escape speed of the universe.
B) the universe is expanding at a rate less than the escape speed of the universe.
C) the universe is expanding at a rate greater than the escape speed of the universe.
D) the universe is expanding at a rate equal to the speed of light.
E) the universe is expanding at a rate greater than the speed of light.
A
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The Moon's angular diameter in our sky as observed from Earth is measured to be 0.5°. From this, we can find the diameter of the Moon in kilometers if we also know the Moon's
a. distance from the Earth. b. element composition c. distance from the Sun.
If an object's mass (M) is doubled, the gravitational force between it and other objects will be
A. increased by a factor of 2. B. decreased by a factor of 4. C. increased by a factor of 4. D. decreased by a factor of 2.
If satellite A is in a 2:1 resonance with satellite B, this means that:
A) satellite A is twice as large as satellite B. B) satellite A moves twice as fast as satellite B. C) satellite A completes one orbit for every two orbits of satellite B. D) the orbit of satellite B takes twice as long to complete as that of satellite A. E) satellite B spins on its axis one time for every two orbits of satellite A.
A 0.20-kg object attached to the end of a string swings in a vertical circle (radius = 80 cm). At the top of the circle the speed of the object is 4.5 m/s. What is the magnitude of the tension in the string at this position?
A. 7.0 N B. 2.0 N C. 3.1 N D. 5.1 N E. 6.6 N