The gravity of
Answer each of the items
below by selecting the best possible choice to complete the sentence.
(A) The moon orbits the Earth in a nearly circular path and does not fall
to the earth because
(B) A news station shows a video of an astronaut in a space station. She is
demonstrating a tool that she used to make a repair to the station during a
spacewalk. When she releases the tool it floats in the air next to her. The
reason it does this is:
- It feels the Earth’s
- The net force on it is zero.
- It is beyond the pull
of Earth’s gravity.
- It is being pulled by the Sun and planets as well as by the Earth.
- It is moving with an appropriate velocity.
- None of the above.
(C) In Star Wars IV, Luke Skywalker is seen dropping an object on the planet Tatooine. If the
video is analyzed to determine the acceleration of the falling object, one
discovers that g = 9.80 m/s2, the same as one would find on earth. However,
the radius of Tatooine is approximately twice that of the earth. A justification
that gTatooine ≈ gEarth is
- There is no gravity in the space station.
- The tool and the astronaut are both in free fall.
- The gravity of the astronaut cancels the gravity of the earth on the tool.
- The net force on the tool is zero.
- They are both moving at the same high velocity.
- The value of g is a constant in all situations.
- Tatooine has 2 suns and 3 moons.
- The mass of Tatooine is four times that of earth and cancels the effect
of the larger radius.
- Luke is using his Jedi powers to alter the value of g.
- The movie was outsourced and actually filmed in Bollywood (Mumbai, India).
Page last modified
December 11, 2010: GR11