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course Phy 122
7-8 10pm
023.
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Question: `qIn your own words explain how the introductory experience with scotch tape illustrates the existence of two types of charge.
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Your Solution:
The experiment showed that there are two types of charges and if you have the right type of charge on two objects then they will attract each other like the two pieces of tape leaned toward each other. If you have charges that repel one another then the two charged objects will distance themselves from one another.
confidence rating #$&*:
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Question: `qIn your own words explain how the introductory experience with scotch tape supports the idea that the force between two charged particles acts along a straight line through those particles, either attracting the forces along this line or repelling along this line.
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Your Solution:
This experiment showed that the charge particles act along a straight line because the parts of the tape that were attracting, for example, attracted directly across from one another instead of attracting to random other parts of the tape. This also worked with the revulsion. When the two pieces repelled one another they didn’t repel at opposite ends of the tape only, for example, they repelled against whatever end of the opposite tape that was near them at that time.
confidence rating #$&*:
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Question: `qIn your own words explain why this experience doesn't really prove anything about actual point charges, since neither piece of tape is confined to a point.
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Your Solution:
The pieces of tape had the same charge throughout the particular side of the tape and they represent a large surface with the same charge throughout the surface thus they did not prove anything about point charges.
confidence rating #$&*:
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Question: `qIf one piece of tape is centered at point A and the other at point B, then let AB_v stand for the vector whose initial point is A and whose terminal point is B, and let AB_u stand for a vector of magnitude 1 whose direction is the same as that of AB_u.
Let BA_v and BA_u stand for the analogous vectors from B to A.
Vectors of length 1 are called unit vectors.
• If the pieces attract, then in the direction of which of the two unit vectors is the tape at point A pushed or pulled?
• If the pieces repel, then in the direction of which of the two unit vectors is the tape at B pushed or pulled?
Explain.
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Your Solution:
From the perspective of point A, if the pieces attract, then point A is pulled to point B and since AB_v is the vector for the movement from A to B and AB_u is the unit vector then A moves toward B.
From the perspective of point B, if the pieces repell, then point B is pushed away from point A. Since BA_v is the vector for the movement from B to A and BA_u is the unit vector then B moves away from A.
confidence rating #$&*:
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Given Solution:
If the pieces attract, then the tape at point A is pulled toward point B.
• The vectors AB_v and AB_u point from A to B.
• Of these the vector AB_u is the unit vector.
• So the tape at A experiences a force in the direction of the vector AB_u.
If the pieces repel, then the tape at point B is pushed away from point A.
• The direction of the force is therefore from A towards B.
• The direction is therefore that of the vector AB_u.
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Self-critique (if necessary): OK
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Self-critique Rating: OK
&#Very good work. Let me know if you have questions. &#