What’s your angle?

 

Objective:  Use a protractor to determine the angle of the sun in your sky. 

 Materials:  Protractor, 1 meter shadow stick and jar of sand, level, roll of string, several hands (people), sun shadow data chart, compass, tape measure, chalk, macadam surface.

 

Procedure:   

  1. Using the chalk on the macadam, draw a straight east/west line using your compass as a guide. 
  2. Draw the shadows listed on the data chart exactly the same length and direction as they were originally measured.
  3. Place your jar of sand and vertical meter stick at the bottom of each shadow mark.  Make sure the stick is perfectly vertical using the level.
  4. Have one person hold a piece of string at the top of the stick.  Have another person hold the rest of the string tightly down to the end of the “chalk shadow.”  (Note:  if the string is not tightly held the angle will be wrong)
  5. Hold the protractor up next to the string on the ground to determine what angle the shadow makes on the ground. 
  6. Record the shadow in a data table recording the latitude, length of shadow, and angle of measurement.
  7. Find the two locations with angles which are closest to being equal.  What other data on the table was nearly the same for these two locations?
  8. Which two locations had angles which were most different from each other?  What other data was very different on the table for these two locations.

Additional Activity I:  You can use the angles of your shadow at the equinox to roughly determine your latitude!  Since you determined the angle of the sun’s shadow above, and the angle of the shadow to the vertical pole is a right angle (90°), you can determine the third angle (angle B below).  Remember, that the sum of all the angles of a triangle is 180°.  This angle should be roughly near the latitude of the measurement.  This trick can only be performed on the two equinoxes!  Try it out.

Additional Activity II:

 

Can you develop another technique for measuring the sun’s angle using the chalk, meter stick, and protractor but not the string?  Describe and draw your technique.  Test it to make sure you get the same angle as you did with the string.

 Hint:  The meter stick does not always need to be vertical.