# Homework Assignment #3

Name:

Section number:

Date Due: Sept. 29

1. A cinder block can be weightless in space. But would you want to kick it with your bare foot? Even if it is weightless, does it still have mass?

2. How many times greater is the Earth's gravitational force on the Moon, than the Moon's gravitational force on the Earth? Think about Newton's third law of motion before answering this question.

3. Calculate the escape velocity (in km/sec) on Mars. How does this compare to the escape velocity on Earth?

4. An earth satellite has a circular orbit (275 km altitude) and an orbital period of 90 minutes. (a) Calculate the centripetal acceleration (in m/s2) experienced by the satellite. (b) Using the modified form of Kepler's Third Law, calculate the Earth's mass from the satellite's orbital period. Show your work.

5. A communications satellite placed into geosynchronous orbit has an orbital period of exactly 24 hours (and appears motionless from the ground below). Calculate the radius (in km) necessary to achieve such an orbit.

6. The broadcast frequency of Wisconsin Public Radio station WERN is 88.7 Megahertz (8.87 · 107 Hz). What is the signal's wavelength in meters?