Physics quiz answers

Posted on August 26, 2007 by Steve

Here are the answers to the quiz:

True statements:
  • The mass of an object is not related to the rate at which it falls.
  • Electricity is the result of electrons moving through a conductor.
  • Ponds form a skin of ice on their surface because ice is less dense than fluid water.
  • Ignoring air resistance, an object dropped into a tunnel through the center of the earth would oscillate from end to end indefinitely.

    Misconceptions:
  • Light coming from the sun is parallel.
  • An aircraft wing creates lift because air has to travel farther over the top surface than the bottom.
  • Sound travels better through solids.
  • A lemon can be used to light a flashlight bulb.
  • Infrared light is a form of heat.
  • Re-entering spacecraft are heated by friction with the air.

    It should be recognized that some of the misconceptions are partly true -- such as that there do exist parallel paths of light between the sun and Earth. And they may be false in ways that are obvious to a casual student of physics.

    I created the true statements and tried to make them as unambiguous as possible, but my definition of electricity could be better.

    Here is the debunking of the misconceptions that inspired the quiz.
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    Comments

    Posted by Eric Phillips | August 27, 2007 | 11:05:01

    Wow. Apparently my junior high science book was wrong about airplane wings. I remember that exact diagram, and the term "Bernoulli Effect." What will I use that term for now? What DOES it do, if not make airplanes fly?

    The air-friction one was a little misleading, I think, because friction DOES heat the re-entering craft, just not as much (according to what I just read at your link) as air compression does. Still, I didn't know that second part.

    As for the object oscillating forever through a trans-planetary tunnel... I was about to complain that this would be a perpetual motion machine. Then I remembered the orbits of the planets, and the "drifting forever in space" phenomenon. Funny how a vacuum changes things.
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