Astr 101 – Homework Assignment #1
Newton's Laws and Gravity

Answer the following questions, using full English sentences. Answers should be no more than 4 lines long, and they must all fit in one page.

(1) What did Kepler's laws say about the shape of the orbit of a planet around the Sun, and the speed at which the planet moves along its orbit?

(2) Now that we understand why planets move the way they do around the Sun, we know that in the Solar System the orbits of planets are not exactly like Kepler said they were. Give an example, and explain why this happens.

(3) Why is Isaac Newton important in the history of astronomy?

(4) Suppose you entered a vacuum chamber, in which there is no air, and dropped a hammer and a feather from the same height. Which one would reach the ground first, and why?

(5) Suppose you see a star with a planet at the same distance from it as our distance from the Sun, but the planet takes less than a year to orbit the star. Is that star more massive than the Sun, less massive, or equally massive? Explain.