In this lesson our instructor talks about gravity and orbits. He discusses law of universal gravitation, gravitational field, orbits, and the 'falling' moon. Four complete example problems round up this lesson.
The force of gravity is based off of the mass of the objects involved (m1, m2), the distance between the objects (r), and the universal gravitational constant (G).
| = G ·
The universal gravitational constant is
G = 6.67 ·10−11 N ·
The force of gravity acts on each object equally, and the direction of the force is towards the center of the other object.
A gravitational field is an area we can treat as having a constant acceleration. Like the surface of the Earth, in some places the force will only change a negligible amount in the area around the object's location.
We denote a gravitational field with ag. Thus, for an object of mass m in the field, Fg = m ·ag.
If we want to find the gravitational field for a given object with mass M at distance r, it is
ag = G ·
If something is in orbit, it must have a centripetal force to keep it in the orbit. Gravity provides this centripetal force. For a simple circular orbit where one object is much more massive than the second object, it follows the relation
Gravity & Orbits
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
This book includes a set of features such as Analyzing-Multiple-Concept Problems, Check Your Understanding, Concepts & Calculations, and Concepts at a Glance. This helps the reader to first identify the physics concepts, then associate the appropriate mathematical equations, and finally to work out an algebraic solution.