Al Tobias (wat4y) - Office: Rm. 201, (434) 924-0538 - Lab: Rm. 202, (434) 924-6800
Demonstrations are cataloged according to PIRA Bibliography
PLEASE REQUEST DEMOS WELL IN ADVANCE
Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.
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Strings and SpringsPurpose:A non-intuitive example of how spring constants add when springs are connected in series and parallel.Procedure:A ball is held up by two identical springs which are connected in the center by a small string of length s (see picture below). Two strings of length L are added, one connecting the bottom string to the support and the other connecting the top spring to the ball. There is no tension in either of these strings. The question is, when the small string "s" is cut, where will the ball end up after it comes to equilibrium?Hints:For this demo, use:
The net change in the distance of the weight from the top is: L - leq - s - 3mg/2k where leq is the equilibrium length of the spring, and a positive result means an increase in distance from the top. Disregarding leq, we can already see that the result is negative so: The ball rises!  |