Conceptual Physics (12th Edition)

Published by Addison-Wesley
ISBN 10: 0321909100
ISBN 13: 978-0-32190-910-7

Chapter 9 - Think and Discuss: 109

Answer

Astronauts are weightless because they are in free fall and there is no support force. This is discussed on pages 166-167. The gravitational field of Earth is definitely not zero at that height. One can calculate g at the approximate height of the ISS. $$g= G \frac{M_{Earth}}{d^{2}} = (6.67 \times 10^{-11} \frac {N \cdot m^{2}}{kg^{2}}) \frac{(6.0 \times 10^{24} kg)}{((6380 + 400) \times 10^{3} m))^{2}}$$ $$g= 8.7 \frac{m}{s^{2}} $$ This is not zero. If Earth's gravity at that height were zero, the ISS would feel no force, and move in a straight line at constant velocity.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.