dis3-slides

dis3-slides - ASTR 100 Discussion 3 Sep. 26, 2011 1....

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Unformatted text preview: ASTR 100 Discussion 3 Sep. 26, 2011 1. Imagine that you're discussing ASTR 100 with your best friend, who has not taken an astronomy class. He/she says, Well, of course the Sun would always have more gravitational force on other objects than the Earth does because the Sun has more mass. Is his/her statement completely correct? If so, explain why. If not, explain what's wrong with the statement, or how it could be made completely correct, and why. Answer: The following is an excellent answer by a student: In general, it is correct, but not completely. Although mass plays an extremely crucial role in determining gravitational force, the distance between two masses also needs to be taken into consideration. The formula for gravitational force is F = GM 1 M 2 /d 2 . Therefore, distance has a small but significant enough role in computing gravitational force. For instance, the Earth has more of a gravitational force on us than the Sun because we are much closer to the Earth than we are to the Sun. Grading checklist: Did you state whether your friend's statement was completely correct or not? Did you explain how mass and distance are both important in gravitational force? Did explain what was wrong with your friend's statement? 2. As the planets orbit the Sun, the Earth and Venus occasionally get relatively close together. What is the gravitational force between the Earth and Venus when they are as close together as they can be? At that time, they are 4 x 10 10 m apart, and Venus's orbital period is 1.6 times smaller than the Earth's. The Earth's mass is 6 x 10 24 kg, and Venus's mass is 5 x 10 24 kg. The gravitational constant is 7 x 10-11 N m 2 /kg 2 . Show your work. Your answer must be in proper scientific notation no fractions. Answer: The equation for the force of gravity is F = GM 1 M 2 d 2 G is the gravitational constant. M 1 is the mass of the Earth, 6 x 10 24 kg. M 2 is the mass of Venus, 5 x 10 2 kg. d is the distance between their centers,...
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dis3-slides - ASTR 100 Discussion 3 Sep. 26, 2011 1....

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