Practice Universal Gravitation
Name
‫ܨ‬௚ =
ீ௠భ ௠మ
௥మ
మ
‫ = ܩ‬6.67 × 10ିଵଵ ಿ∙೘
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1. Suppose that two objects attract each other with a gravitational force of 16 N. If the distance between the two
objects is doubled, what is the new force of attraction between the two objects?
2. Suppose that two objects attract each other with a gravitational force of 16 N. If the distance between the two
objects is reduced in half, then what is the new force of attraction between the two objects?
3. Suppose that two objects attract each other with a gravitational force of 16 N. If the mass of both objects was
doubled, and if the distance between the objects remained the same, then what would be the new force of
attraction between the two objects?
4. Suppose that two objects attract each other with a gravitational force of 16 N. If the mass of both objects was
doubled, and if the distance between the objects was doubled, then what would be the new force of attraction
between the two objects?
5. Use Newton’s Law of Universal Gravitation to determine the mass of someone who has a weight of 732 N. The
mass of the earth is known to be 5.98 x 1024 kg, and the distance to the center of the earth is 6.4 x 106 m.
6. Use your answer from the previous question to determine the person’s mass using Newton’s 2nd Law, Fw = mg.
7. Calculate the distance between two 75 kg masses that have a gravitational attraction of 8.34x10-7 N.
8. Determine the force of gravity on 65 kg astronaut in the space station. The space station is known to be 6800 km
(6.8 x 106 m) from the earth’s center, and the mass of the Earth is 5.98 x 1024 kg.
9. Determine the force of gravity between you and your friend who is sitting a distance from you of 0.50 m. (If you
don’t know your mass and your friend’s mass, use 49 Kg for both).
10. Having recently completed her first Physics course, Dawn Well has devised a new business plan based on her
teacher's Physics for Better Living theme. Dawn learned that objects weigh different amounts at different
distances from Earth's center. Her plan involves buying gold by the weight at one altitude and then selling it at
another altitude at the same price per weight. Should Dawn buy at a high altitude and sell at a low altitude or
vice versa?
11. Anita Diet is very concerned about her weight but seldom does anything about it. After learning about Newton's
law of universal gravitation in Physics class, she becomes all concerned about the possible effect of a change in
Earth's mass upon her weight. During a (rare) free moment at the lunch table, she speaks up "How would my
weight change if the mass of the Earth increased by 10%?" How would you answer Anita?
12. When comparing mass and size data for the planets Earth and Jupiter, it is observed that Jupiter is about 300
times more massive than Earth. One might quickly conclude that an object on the surface of Jupiter would weigh
300 times more than on the surface of the Earth. For instance, one might expect a person who weighs 500 N on
Earth would weigh 150000 N on the surface of Jupiter. Yet this is not the case. In fact, a 500-N person on Earth
weighs about 1500 N on the surface of Jupiter. Explain how this can be.