Where here we have used the [[184_notes:math_review#Unit_Vectors|definition of the unit vector]] (ˆr=→rr) to get the two different versions of the equation. There are a few things to notice about this equation. First, this equation is **only true for the electric force between two point charges**. Second, this force is **not a constant force** - it depends on the separation distance between the two charges. The closer the two charges are, the stronger the push/pull will be. Finally, this equation may look familiar from mechanics - if you change the charges into masses and change the constant, you will get the equation for [[183_notes:gravitation|Newtonian gravity]] that describes the gravitational interaction between two large masses. It turns out that there are many parallels between the gravitational force and the electric force.
+
Where here we have used the [[184_notes:math_review#Unit_Vectors|definition of the unit vector]] (ˆr=→rr) to get the two different versions of the equation. There are a few things to notice about this equation. First, this equation is **only true for the electric force between two point charges**. Second, this force is **not a constant force** - it depends on the separation distance between the two charges. **The closer the two charges are, the stronger the push/pull will be.** Finally, this equation may look familiar from mechanics - if you change the charges into masses and change the constant, you will get the equation for [[183_notes:gravitation|Newtonian gravity]] that describes the gravitational interaction between two large masses. It turns out that there are many parallels between the gravitational force and the electric force.
==== Examples ====
==== Examples ====
[[:184_notes:examples:Week3_balloon_wall|Ballon Stuck to a Wall]]
[[:184_notes:examples:Week3_balloon_wall|Ballon Stuck to a Wall]]