2.  Force: a push or a pull  Shooting a basketball  pushing the ball  Pulling a desk across a room  Contact Forces: forces that have an effect ONLY on the objects that they touch  See above examples

3.  Electric Force: a push or pull between charged objects  Action-at-a-distance Forces: can apply force to an object without touching it  Ex. Electric Force

4.  In the past, action-at-a-distance charges were used to see how the 3 types of charges (+, -, neutral) interacted  DISCOVERY!  2 +ively charged objects would repel each other  2 –ively charged objects would repel each other  When +ively and –ively charged objects were attracted to each other  Charged objects (+/-) were attracted to neutral objects

6.  Laws of Static Charge:  Like charges repel  Opposite charges attract  Neutral objects are attracted to charged objects  Charles Coulomb: electric force is proportional to charge  Increase the amount of charge, increase the amount of electric force  Decrease the amount of charge, decrease the amount of electric force  Increase the distance between charged objects, decrease the electric force  Decrease the distance between charged objects, increase the electric force

7.  The charging of a neutral object by touching it to a charged object  Transferring charge between objects through touching or rubbing  Example: Electroscope  When a negative object touches a neutral electroscope, electrons spread evenly over the metal leaves  repel because of negative charge

8.  The rearranging of electrons on a neutral object by bringing a charged object close to it  Example:  A negatively charged object will repel electrons in the knob  Because it’s a conductor, the electrons will move down to the leaves which will repel

9.  Induction explains why neutral and charged objects attract each other  Balloon becomes negative after being rubbed in hair  Place balloon against the wall ▪ the negative wall charges are repelled, leaving that part of the wall positive (attracting the balloon)

10.  See Figure 7.14 (pg. 261) in Chapter 7 of textbook!