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Sample Old Exam 1

  1. Gravity:

    a. Calculate the gravitational force exerted by planet Earth on a hypothetical college student who is sitting in a chair in SC 5326 taking an Astronomy 101A midterm exam on the campus of Vanderbilt University. Assume the mass of the student is 50 kg.

    b. Convert your answer from Newtons to pounds (1 pound = 4.438 Newtons). This force obviously is the student's weight.

    c. What is the force exerted by the student on the planet Earth?

    d. How do these two forces compare? (one or a few words will do)

    e. If the radius of Earth were twice as big but the student's and Earth's total masses were unchanged and the student still sat on the surface of this new Earth, would the student weight more or less than now?

    f. Qualitatively or conceptually, explain why his/her weight does or does not increase or decrease.

  2. Martian Moons:

    a. What one word describes the shape of the orbit of Mars' moon Phobos.

    b. If you knew nothing about gravity, but knew about Galileo's experiments on moving objects and/or Newton's laws of motion, you would know that a force is acting on Phobos. Why do you know this?

    c. Mars has two moons, Phobos and Deimos. If you were to calculate the accelerations of these two moons in their orbits, you would you need to know the numerical values of certain parameters. Which parameters would you need to know?

    d. Which moon experiences the smaller acceleration? How much smaller?

    e. Phobos revolves around Mars in 0.319 days (7 hours, 39 minutes, 22 seconds). Without any other numbers other than those available to you on these exam sheets plus whatever wisdom you have brought with you in your head, deduce the most likely rotation period of Phobos? (Give a numerical answer.)

    f. Explain the reasoning you used to determine your result for part e.

  3. We have discussed and you have read about the most accepted theory of how the solar system formed. Our theory depends on certain dynamical, chemical, and temporal (age) constraints as determined by observations and experiments carried out by astronomers and planetary scientists. As part of this theory, we surmised that our solar system is probably typical of most or all planetary systems that we might some day discover around other stars. If this is a good scientific theory, it must be logically falsifiable.

    a. What does the term "logically falsifiable" mean? You may use examples if it helps you explain, although you do not need to present examples.

    b. Imagine your grandchildren sitting in this classroom (probably remodeled by then), listening to the aged, 85 year old Professor Weintraub describe the origins of our solar system and planetary systems in general. You are startled because the theory he describes is quite different from that which he taught to you. He says that the planets were formed inside the Sun and expelled into their orbits by the medium range, gravonuclear force. Using your understanding of what science is, how science works, and of scientific theories, describe what might have happened in the intervening 50 years?