Newton and the Law of Universal Gravitation Quiz Answers: Select the correct answer to complete the sentence. Gravitational force is said to be universal because..
1. A. It applies to all objects.

Why does the speed of a planet decrease as it moves away from the sun?
2. C. The direction of the sun's pull relative to the planet's motion changes.

Which statement about the development of Newton's theory of universal gravitation is correct?
3. A. Isaac Newton described the existence of gravitational force mathematically, but he built upon the ideas of other scientists before him.

Drag each item to the correct location, so that each contribution to the theory of universal gravitation is matched with the scientist responsible for it.
4. Johannes Kepler: Described the motion of planets around the sun as elliptical.
Robert Hooke: First proposed the idea that a force of attraction applied to all objects in space.
Isaac Newton: Used mathematics to prove that gravity increases with decreasing distance between objects.

Drag each item to indicate whether it is related to Aristotle's of Ptolemy's model of the solar system, or to both. Some items may be used twice.
5. Aristotle's Model: Geocentric, Planets fixed on nested places.
Ptolemy's Model: Accurately predicted the positions of the planets, Planets fixed on epicycles, Geocentric.

Which of the eight planets in the solar system has the most elliptical orbit?
6. B. Mercury

Drag each item to the correct location.
7. Geocentric Model: Earth is at the center of the solar system, The orbits of the planets are circular, Includes five planets.
Heliocentric Model: The sun is at the center of the solar system, The orbits of the planets are elliptical, Includes eight planets.

Why was the Copernican model a controversial proposition? Select the three correct answers.
8. A. It contradicted religious doctrine of the time.
B. It contradicted established scientific understanding.
E. It demoted Earth to just another planet.