Site MapHelpFeedbackGravity and Motion
Gravity and Motion


<a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=jpg::::/sites/dl/free/0072509856/220722/chapter2.jpg','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (169.0K)</a>
  • Gravity controls the motion of most astronomical objects.
  • If no forces act on an object, inertia keeps it moving in a straight line at a constant speed.
  • If an object is not moving along a straight line at a constant speed, a force must be acting on it.
  • Newton’s laws of motion allow us to describe and predict an object's motion if we know the forces acting on it.
  • The force of gravity between two objects depends on their mass and the distance between them:
    • The greater their separation, the weaker the force.
    • The greater their mass, the greater the force.
  • Orbital motion allows us to determine the mass of (“weight”) astronomical objects.








To learn more about the book this website supports, please visit its Information Center.
(c)2006 McGraw-Hill Higher Education
Any use is subject to the Terms of Use and Privacy Policy.
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.


ExplorationsOnline Learning Center

Home > Chapter 2