Joe attaches a spring to a post in his backyard. The spring is free to rotate around the post. The force constant of the spring is k = 10 N/m. He makes a map of several locations in his yard, using a grid with boxes of size 1 meter.
Joe tries moving the end of the spring to different locations.
distance from spring must SPE
location post (m) stretch by (m) (J)
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A
B
C
D
E
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Right. Joe decides to make a map showing the spring potential energy at each of these locations.
Suppose that Joe moves from one location to another. What is the change in SPE as he moves?
change in
from to SPE (J)
------------------------------------
A B
A C
A D
D E
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After moving around for a while in the back yard, Joe recognizes a pattern: if he moves around the pole in a circular pattern, the spring potential energy remains constant.
Joe compares the change in SPE to his displacement from one point to another. He decides to compute a quantity he calls Q
change in SPE (J)
Q = --------------------
displacement (m)
What are the units of this combination?
Compute this quantity for:
from to change in SPE displacement Q
(J) (m)
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A B
A D
D E
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Use positive numbers to mean "away from the post" and negative numbers to mean "towards the post" in the following.