Planets would crash into the Sun if it weren't for
A) their tangential velocities.
B) their vast distances from the Sun.
C) the inverse-square law.
D) their relatively small masses.
E) the fact that they are beyond the main gravitation of the Sun.
Answer: A
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A can, after having been given a kick, moves up along a smooth hill of ice. It will
A) have a varying acceleration along the hill. B) have the same acceleration, both up the hill and down the hill. C) have a constant acceleration up the hill, but a larger constant acceleration when it comes back down the hill. D) have a constant acceleration up the hill, but a smaller constant acceleration when it comes back down the hill. E) travel at constant velocity.
The Hertzprung—Russell diagram is a plot of
A) radial velocity against distance B) apparent brightness against time C) luminosity against distance D) luminosity against surface temperature
All gamma-ray bursters have the same fundamental driving mechanism, although we don't yet know whether it is a hypernova or a merger of two neutrons stars
Indicate whether the statement is true or false
Velma and Mort pass each other, in rocket ships, at a relative velocity of half of lightspeed. Velma has an ice cream cone which will melt in 5 minutes if not refrigerated. She removes her cone from the refrigerator, and allows it to melt
According to Mort, how long does it take for Velma's cone to melt? A) more than 5 minutes B) less than 5 minutes C) 5 minutes D) It could be either more than 5 minutes, or 5 minutes, depending on which observer is at rest. E) It is impossible to answer this question, because such measurements of moving objects have no precise meaning.