Gravitational Force
We are all familiar with the force of gravity. It is a
fundamental observed property of our universe that any two masses
and
experience an attracting force
given by the
formula
where
![$ r(t)$](http://www.dsprelated.com/josimages_new/pasp/img2617.png)
![$ m_1$](http://www.dsprelated.com/josimages_new/pasp/img2292.png)
![$ m_2$](http://www.dsprelated.com/josimages_new/pasp/img2615.png)
![$ t$](http://www.dsprelated.com/josimages_new/pasp/img122.png)
![$ G$](http://www.dsprelated.com/josimages_new/pasp/img99.png)
The law of gravitation Eq.(B.2) can be accepted as an
experimental fact which defines the concept of a force.B.3 The giant conceptual leap taken by Newton was that the law of
gravitation is
universal--applying to celestial bodies as well as objects on
earth. When a mass is ``dropped'' and allowed to ``fall'' in a
gravitational field, it is observed to experience a
uniform acceleration proportional to its mass. Newton's second
law of motion (§B.1) quantifies this result.
Next Section:
Hooke's Law
Previous Section:
Mass