Eggs: Yummy and Great Science!
Author(s): Jon Fisher and Rosalie Van Zyl
Discrepant Event - Teacher's Guide
SED 695B; Fall 2005
 
Detailed Explanation of Discrepant Event

Principles illustrated

  • Center of Gravity
  • Friction
  • Kinetic Energy
  • Inertia

There are four different discrepant events here:

1. Spinning a hard-boiled egg vs. an uncooked egg

Spin an uncooked egg and a hard-boiled egg. You will notice that they spin at different rates. The hard-boiled egg will spin faster.

2. Spinning an uncooked egg, stopping it, then letting go again and it continues spinning

3. Spinning a hard-boiled egg so it eventually "stands up" while spinning

In order to accomplish this you must spin the hard-boiled egg rapidly

4. Standing an uncooked egg up (on days other than the equinox!)

Patience!

 

Standards

8th Grade Physical Science

  • Students know how to identify separately the two or more forces that are acting on a single static object, including gravity, elastic forces due to tension or compression in matter, and friction.
  • Students know that when the forces on an object are unbalanced, the object will change its velocity (that is, it will speed up, slow down, or change direction).
  • Scientific progress is made by asking meaningful questions and conducting careful investigations. Students will plan and conduct a scientific investigation to test a hypothesis
 

Questioning Script

Prior knowledge & experience: Students have probably learned somewhere that in order to tell the difference between a hard-boiled egg and a non-cooked egg is by spinning them.

Root question #1: How can you tell the difference between a hard boiled egg and an uncooked egg?

Target responses #1: You spin them. The hard- boiled egg will spin very fast, while the non-cooked egg will spin more slowly.

Root question #2: Why does a spinning hard-boiled egg stand up?

Target responses #2:When the egg spins, there is a slight bit of friction between the egg and the surface it is spinning on. That friction slows the egg down enough to force it vertical and continue spinning.

Prior knowledge & experience: Students have probably at some time in their elementary school lives tried to stand an egg up on the vernal equinox. Since they have performed this experiment or watched the news on that day, they may think that that is the only time that eggs stand up.

 

Root question #3a: Why are you unable to stand a hard-boiled egg up, while you can with a non-cooked egg?

Root question #3b: Why are you able to stand up an uncooked egg on any day of the year - if you have the patience?

Target responses #3a:The inside of the hard-boiled egg is solid so it cannot move. Because of this, the egg cannot "adjust" its center of gravity to accommodate this ak ward upright position. The uncooked egg will stand up especially if you shake it to free the yolk to move about.

 

Common Misconceptions: The common misconception is that the non-cooked egg only stands up on the equinox (vernal not autumnal) due to gravity of the sun being right over our heads.

 
Why do these eggs stand up? Are these raw eggs or hard-boiled eggs? Must it be the vernal equinox when this picture was taken?
Why does the egg on the left seem to be experiencing vertigo? What is post-rotary nystagmus and how might this apply to the egg on the right?
 
   

References & Links:

Spinning Eggs to make them stand on their heads

Ian Reed's Science Wizard - Eggs and Inertia

Misconceptions - about eggs and the equinox