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 = 20 N/m**.
He makes a map of several locations in his
yard, using a scale of 1:100.

- What is the rest length of the spring?

Joe tries moving the end of the spring to different locations.

distance from spring must SPE location post (m) stretch by (m) (J) --------------------------------------------------------- A B C D E G ----------------------------------------------------------

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 D E G C ------------------------------------

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) -------------------------------------------------------- G C --------------------------------------------------------

Use positive numbers to mean "away from the post" and negative numbers to mean "towards the post" in the following.

- What is the force exerted by the spring when Joe stands at G?
- What is the force exerted by the spring when Joe stands at C?
- What is the force exerted by the spring when Joe stands halfway between G and C?