# Week 17 (Dec. 2 - 6)

**Reading:**PSE Chap 14 gravity

**Topics:**Newton's law of universal gravitation

**No quiz this week**

**Week 17 Homework Problems:**

**Orbiting ISS Problem:**Earth's moon orbits earth at a distance of 60 earth radii from the center of the earth; the moon takes about 28 days to orbit once. The international space station orbits earth at an altitude of 400 km above earth's surface. What is its orbital period (in hours). Hint: use Kepler's third law of planetary motion.**Meteor problem (****solution****):**A dangerous meteor flies past the Earth. It passes a distance of 5 earth radii from the surface of the earth. What is the acceleration of the meteor at this distance?**Mass of Jupiter (****solution****):**Io, a small moon of Jupiter, has an orbital period of 1.77 days and an orbital radius of 4.22 x 10^5 km. From this data, determine the mass of Jupiter.**Optional calculus/challenge problem:**A very thin 10 meter long lead rod is curved into a semi-circle. The total mass of the bar is 100 kg. A small lead ball of mass 1 kg is placed at the center of the semi-circle, equidistant from every point on the bar. What is the gravitational force exerted by the bar on the ball? Hint: you will need to sum up the force of gravitational attraction on the ball from each little segment of the rod by integrating.