Teaching Physics with the Physics Suite Edward F. Redish Problems Sorted by Type | Problems Sorted by Subject | Problems Sorted by Chapter in UP

The gravity of the situation

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

1. It feels the Earth’s gravitational pull.
2. The net force on it is zero.
3. It is beyond the pull of Earth’s gravity.
4. It is being pulled by the Sun and planets as well as by the Earth.
5. It is moving with an appropriate velocity.
6. None of the above.
(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:
1. There is no gravity in the space station.
2. The tool and the astronaut are both in free fall.
3. The gravity of the astronaut cancels the gravity of the earth on the tool.
4. The net force on the tool is zero.
5. They are both moving at the same high velocity.
(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
1. The value of g is a constant in all situations.
2. Tatooine has 2 suns and 3 moons.
3. The mass of Tatooine is four times that of earth and cancels the effect of the larger radius.
4. Luke is using his Jedi powers to alter the value of g.
5. The movie was outsourced and actually filmed in Bollywood (Mumbai, India).