The tropical year is shorter than the sidereal year because Earth's
a. orbit is an ellipse rather than a true circle.
b. axis precesses westward.
c. orbital speed is not constant.
d. axis is tilted by 23.5°.
b
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A quantity that is measured in ohms is
a. voltage b. current c. resistance d. electric field e. critical temperature
In the afternoon, the decibel level of a busy freeway is 80 dB with 100 cars passing a given point every minute. Late at night, the traffic flow is only 8 cars per minute. What is the late-night decibel level?
a. 77 dB c. 70 dB b. 74 dB d. 69 dB
We can't detect stellar parallax with naked-eye observations. Which of the following would make parallax easier to observe?
A) increasing the size of Earth's orbit B) speeding up Earth's rotational motion C) slowing down Earth's rotational motion D) speeding up the precession of Earth's axis E) getting away from streetlights
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
A) Mars rotates much slower than the Earth. B) The Martian core is made of rock, while Earth's core is made of metal. C) Mars's interior has cooled so much its molten core layer no longer undergoes convection. D) Mars is too far from the Sun to have a global magnetic field.