River Physics
by Joe Riederer

The woman driving the tan Subaru smiled as she passed me in the next lane. Her car had two fiberglass canoes on the roof and fishing poles pressed against the rear window. The bumper sticker, half-covered with mud, proclaimed, "I'd rather be canoeing." Having just spilt coffee on a stack of papers I corrected the night before, all I could think of was, "Me too!" Anyone seeing our two vehicles would immediately know I was heading to work and she was about to have an adventure. Crossing the Wisconsin River on my way to a windowless classroom, I looked longingly down stream.

The traffic light on the far side of the bridge turned red and the obedient line of cars came to a robotic stop. I was trapped with this enticing river on both sides and that nagging bumper sticker in front of me. A trio of duck made a sharp banking turn and landed near a small island that split the river into two channels.

The light turned green, but that simple message continued to taunted me--I'd rather be canoeing. Unfortunately, I couldn't be on the river-I had to teach science. Don't get me wrong, I love teaching science. On most days it's the only thing I would want to do. Today just wasn't one of those days.

When I was younger, before I had a "real" job, I would never pass up a chance to get on the river. Memories flooded my head--running the rapids of the Namekagon, Brule, and Flambeau Rivers, slowly drifting through the cathedral-like elm forests of the Yellow River, climbing the waterfalls on the Potato River, and a childhood spent exploring the polluted Rock River. Today I had to go to work.

What if I could do both? What if I could be on the river AND teach science. I grabbed the nearest piece of paper and furiously began to write (I now had to explain to one of my students why her lab report was covered with coffee stains and my version of shorthand).

What follows is a brief outline of physics topics that could be taught on, or near, a river. Think of it as a River Physics textbook. Understand that this is only a work in progress and there are many gaps, but if it can get me back on the river, while keeping my job, it's worth a shot.

Chapter 1 - Density

  • Why do things float?
  • Archimedes' principle demonstrated by the air bladders in fish

Chapter 2 - Nature of matter

  • Changing states of water in the hydrologic cycle
  • Strength of ice--When is it safe to walk on ice?
  • Frost heaves
  • Surface tension demonstrated by water striders
  • Specific heat of water
  • Water Chemistry

Chapter 3 - Newton's Laws

  • Paddling a canoe

Chapter 4 - Work, Energy, and Power

  • Flowing water as an example of potential and kinetic energy
  • Ice flow damage
  • The physics of beavers--dam building, hydrodynamics, tree cutting
  • Calories burned while canoeing
  • he insulation value of duck down
  • Hydroelectric power plants
  • Movement of particles (sand, silt, clay) by running water
  • Formation of meanders and ox bows
  • Flood damage
  • Simple machines demonstrated in the anatomy of aquatic insects
  • Wrapping a 16-foot Aluminum canoe around a rock while canoeing on the Flambeau River
  • The work involved when the school group you are leading is awoken at 4 a.m. because the dam up stream unexpectedly released water and your sand bar campsite is disappearing fast!

Chapter 5 - Electricity

  • Conductivity used to study water quality
  • Electro-shocking fish for census data
  • Lightning that hits every time I go camping

Chapter 6 - Waves

  • Refraction - waves bend as they move from deep to shallow water at an angle
  • Diffraction - waves passing around rocks
  • Constructive and destructive interference - when two waves combine
  • Reflection - waves reflect off barriers at the same angle they hit

Chapter 7 - Sound Waves

  • Vibrations and the lateral lines of fish
  • Speed of sound in water
  • The power of a boom box to destroy the magic of a riverside camp site

Chapter 8 -Properties of Light

  • Loss of color with increase in water depth
  • Reflection of light off the river surface
  • Mosaic lens of the dragonfly's eye
  • Iridescent colors from spilt fuel
  • Refraction of light by water

Chapter 9 - Motion of Rigid Bodies

  • Center of gravity in puddle ducks compared to diving ducks
  • Skipping stones

Chapter 10 - Mechanical Properties of Matter

  • Laminar and turbulent flow of river water
  • Whirlpools and eddies

Clearly this is not a complete list. It will take much more than this to convince the school board to let me sell the desks and buy Pfd's. If you have suggestions as to how physics could be taught on a river, please email them to me and I will add them to the list. I think it may be time for a new bumper sticker. This one will say, "I'd rather be teaching on the river!"

Joe Riederer

Learn more about Joe, and his novel, "Restoration in the Barrens."

Center for Global Environmental Education
Hamline University Graduate School of Education
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