Spring to Another World Key

							Spring to Another World
This tech lab is a nice companion to “Totally Stressed Out.” It presumes knowledge of
Hooke’s law (Hooke’s law is referred to and given in the procedure. There are some nice
subtleties in the simulation: stronger springs are depicted with thicker wire, and objects
dropped from greater heights impact the “ground” with louder sounds.
The Physics Education Technology Group (PhET) at the University of Colorado at Boulder has
developed dozens of excellent, interactive physics computer simulations. You can find them at
http://phet.colorado.edu. You can download all the PhET simulators from their web site, free of
charge.
The PhET simulator used in this tech lab is “Masses & Springs.” Download and run it before class
to make sure your computers can run it. This tech lab and corresponding key were written using
“Masses & Springs” version 2.01.
Answers to the Questions
PART A: DETERMINATION OF A FORCE CONSTANT
Step 7: F = mg = 0.100 kg · 9.8 m/s2 = 0.98 N
Step 8: x = 10 cm = 0.10 m
Step 9: F = kx => k = F/x = 0.98 N / 0.10 m = 9.8 N/m
PART B: THE RED MATTER
Steps 1-2: Hang the red cylinder from Spring 1 and measure the stretch. Use F = mg = kx,
   solving for m. So m = kx/g. The stretch x should be approximately 30 cm.
   So m = 9.8 N/m · 0.30 m / 9.8 m/s2 .
Step 3: 300 grams
PART C: GRAVITATIONAL ACCELERATION ON PLANET X
Steps 1-2: Hang the 100-g mass from Spring 1 and measure the stretch. Use F = mg = kx,
   solving for g. So g = kx/m. The stretch should be about 3.8 cm.
Step 3: 3.8 m/s2
PART D: THE RANGE OF FORCE CONSTANTS FOR SPRING 3
Steps 1-2: Hang the 100-g mass from Spring 3. Set “softness spring 3” all the way to soft.
   Record the stretch, which should be no more than 53 cm. Then set “softness spring 3” all
   the way to hard. Record the stretch, which should be no less than 1.9 cm
Step 3: About 2 N/m (±0.2 N/m)
Step 4: About 50 N/m (±2 N/m)