Simple Harmonic Motion and Mechanical Resonance (NOTES/IDEAS)

Experiment Outline

Day 1:

  1. Have students build oscillators, with a focus on variety
  2. Class discussion on commonalities between builds
  3. Each group chooses a single system and measure the period
  4. Groups systematically change initial amplitude and see if period is affected
    1. No effect: Possible harmonic oscillator
    2. Effect: Not a simple harmonic oscillator
  5. Move to common system: Mass on a spring
  6. similar measurement of period
  7. Characterize spring constant
  8. Introduce rotary encoder as measurement device

Day 2:

  1. Pick up with spring system again
  2. Introduce air tracks as a way to optimize setup by reducing friction
  3. Students characterize SHO behavior
  4. Students add damping term, characterize changes
    1. How damping interacts with spring constant/mass
    2. How damping affects period
  5. Students add driving term
    1. Investigate frequency/amplitude relationship

Mechanical Resonance Options

  • Option 1 - Use air tracks for all groups
    • Use springs/carts on day 1 as known system
      • Can vary cart mass / spring tension
    • Can add damping & driving day 2
  • Option 2 - Open-ended setup
    • Day 1 - Students given supplies, asked to make something that oscillates, such as:
      • Pendulum
      • Suspended spring
      • Torsion pendulum
      • rocking motion from curved body
      • marble running on semi-circle track
    • Students do something to characterize motion
      • Video analysis with tracker
      • Timing maximum amplitudes
    • Students asked to keep type of system the same but change the period at least twice, in different ways if possible
    • Day 2: Add in discussion/usage of damping and/or driving
      • Damping would be natural in most experiments in some form
      • Driving could be difficult to add arbitrarily
      • Analysis would almost certainly require Tracker and video
  • Option 3 - Hanging springs only
    • Students only work with masses hanging from springs / elastic
    • Make it so that many springs and masses are available
      • Option to use springs side-by-side could be cool
      • Would be easier to use with photogate, maybe.
        • Might have to add a flag to the edge to pass through gate
    • Day 2: Damping/Driving could be done more readily with motors and coupling string/spring

Option 1 Pros:

  • Already have equipment, software, etc
  • Known quantity since we've done it before

Cons:

  • Blowers are pretty loud
  • No meaningful apparatus building

Option 2 Pros:

  • Similar style of apparatus design as other labs this quarter

Cons:

  • Measurement is problematic
  • Need materials quickly

Option 3 Pros:

  • Have equipment already
  • Has a few more options to explore than Option 1

Cons:

  • Still would need to come up with measurement setup
  • Springs will likely die at the hands of students