Physics 212 Week 1
Hands-On 1 (HO-1)
Exploring MagicTM Tape Interactions
Create a WordTM file for your group. Label it by your first names followed by HO-1. Clearly answer all the numbered questions.
Preparing a "U" tape
Use a strip of Scott brand Magic tape about 20 cm or 8 inches long (about as long as this paper is wide). Shorter pieces are not flexible enough, and longer pieces are difficult to handle. Fold over one end of the strip to make a non-sticky handle:
* Prepare a U [for Upper] tape as follows:
· Stick a strip of tape with a handle down onto a smooth flat surface such as a table. · Smooth this base tape down with your thumb or fingertips. This base tape provides a standard surface to work from. (Without this base tape, you get different effects on different kinds of surfaces.) · Stick another tape with a handle down on top of the base tape. · Smooth the upper tape down well with your thumb or fingertips. · Write U (for Upper) on the handle of the upper tape. · With a very quick motion, pull the U tape up and off the base tape, leaving the base tape stuck to the table. |
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Your hand and a U tape
* Hang the U tape vertically from the edge of the table, and bring your hand near the hanging tape.
Note: Numbered Questions are to be answered in your WordTM file for electronic submission.
1. Write a brief description of what happens:
2. What happens if you approach the other side of the tape with your hand?
STANDARD PROCEDURE FOR MAKING OR REMAKING A U TAPE
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3. How do you expect two U tapes to interact with each other? Do you expect them to repel each other, attract each other, or not to interact at all?
* Now prepare a second U tape in exactly the same way (remember to write U on the handle). Bring it near the hanging U tape. Since the hanging tape interacts with your hands, try to keep your hands out of the way. For example, you might approach the vertically hanging tape with the other tape oriented horizontally, held by two hands at its ends.
4. Describe what happens when you bring 2 U tapes together. Does it matter which sides (smooth or sticky) approach each other?
* Suspend a U tape from a thread. Use a short piece of tape to hang the thread from the table. Approach the suspended tape from various directions with another U tape.
· Move a U tape very slowly toward a hanging U tape. Observe the deflection of the hanging tape from its original position, at several distances (for example, the distance at which you first see repulsion, half that distance, etc.) Make a very rough graph of the strength of the repulsive interaction as a function of the distance between the two tapes (you can't really go all the way to 0 distance!) The deflection of the tape away from its original vertical position is a measure of the strength of the interaction.
5. Describe in words the graph you get for repulsive interaction versus distance.
You may have noted several difficulties in making accurate measurements of displacement versus distance. For example, the tapes are both attracted to your hand, as well as repelling each other. If you tried to use a ruler, you may have found that the tapes are attracted to the ruler, too. For now, we'll settle for rough observations, but keep these difficulties in mind.
Modifying a U Tape
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* Make sure you have an active U tape. Hold onto the bottom of the U tape and slowly rub your fingers or thumb back and forth along the slick side of the tape. |
6. Describe the changes in how this modified U tape interacts with your hand and another U tape:
* Prepare two modified U tapes. Hang one of them from the table and note how strongly the other tape repels it. Partially modify one of the tapes by running your finger along the length of the slick side of the tape, being careful that your finger touches only a portion of the width of the tape. Again observe how strongly the two tapes repel.
7. What is the effect of this partial modification?
Making an "L" (lower) tape Here is a reproducible procedure for making an "L" tape.
* Stick a new strip of tape, with a handle at one end, down onto a base tape that is stuck down on the desk. Smooth it down with your thumb or fingertips, and write L on its handle. Then stick another strip with a handle on top of the L tape, smooth it down, and write U on its handle. * Slowly lift the L tape, bringing the U tape along with it (and leaving the bottom base tape stuck to the desk). Hang the double layer of tape vertically from the edge of the desk and see whether there is attraction between it and your hand. If so, get rid of these interactions (hold the bottom of the tape and slowly rub the slick side with your fingers or thumb). * Check that the tape pair is no longer attracted to your hand. THIS IS IMPORTANT! * Hold onto the bottom tab of the L tape and quickly pull the U tape up and off. Hang the U tape vertically from the edge of the desk, not too close to the L tape! * Repeating exactly the same procedure, make another pair of tapes so that you have at least two U tapes and two L tapes. Before separating the two tapes from each other, remember to run your finger along the slick side of the tape pair to get rid of interactions with your hand. |
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8. What interaction would you predict between an L tape and a U tape?
9. Make sure that both the U tape and the L tape are active (attracted to your hand). What interaction do you observe between an L tape and a U tape?
10. What interaction would you predict between two L tapes?
11. What interaction do you observe between two L tapes?
* Move a U tape very slowly toward a hanging L tape. Observe the deflection of the hanging tape from its original position, at several distances (for example, the distance at which you first see repulsion, half that distance, etc.) Make a very rough graph of the strength of the attractive interaction as a function of the distance between the two tapes (you can't really go all the way to 0 distance!) The deflection of the tape away from its original vertical position is a measure of the strength of the interaction.
12. Describe in words your graph between U and L interaction versus distance.
13. Now summarize the interactions you have observed between U and L tapes. [Remember motion of objects occurs in response to forces. Force is a vector. So discuss both the magnitude and direction of the interactions you observed.]