Projects‎ > ‎(1) Discrepant Events‎ > ‎

Inertia & Friction - Quarter Karate (Sabiha Dalal)


Sabiha Dalal, 6th Grade Special Education  Teacher, Sepulveda MS

Principle(s) Illustrated

  1. Principle 1 - Inertia
  2. Principle 2 - Friction
  3. Principle 3 - Newton's 1st Law of Motion


  • Science Standard: 8th Grade Focus on Physical Sciences
  • Forces 2. Unbalanced forces cause changes in velocity. As a basis for understanding this concept:
       a.)Students know a force has both a direction and magnitude
       c.)Students know when the forces on an object are balanced, the motion of the object does      
           not change.  
       d.)Students know how to indetify separately the two or more forces that are acting on a single 
           static object, including gravity, elastic forces due to tenesion or compression in matter, and 
  • Science Standard: 9th -12th Grade Physics
  • Motion & Forces 1.Newton's laws predict the motion of most objects. As a basis for understanding this concept:
       b.)Students know that when forces are balanced, no acceleration occurs, thus an object 
           continues to move at constant speed or stays at rest(Newton's first law).

Questioning Script - (can be adapted with coins, games tokens, rulers)


    1.) 10 quarters

    2.) spatula or finger


1.) Place the stacked coins on a table.

2.) Hold the spatula blade flat against the table and with a quick flick of the wrist, slide the edge of    the blade toward the bottom coin in the stack. Observe what happens. If you don't want to use a spatula you can use your pointer finger to move the coins. 

3.) You can do this with your point finger and a variation of other types of coins as well. 

Prior knowledge & experience:

Students know that friction is a force acting on objects. Also, they know about inertia.  

Root question:

1.) Explain what will happen to a stack of 10-12 quarters that is placed on a table,
     when a spatula blade slides on the edge of the bottom quarter.
2.) What force(s) cause the quarter to stop moving.
3.) Create another way to illustrate inertia and demonstrate it to the class.

Target response:

The bottom coin is ejected and the stack of quarters drops without tipping over. This demonstrates Isaac Newton's First Law of Motion. The spatula provides an external force which causes the bottom coin to move. Friction and air resistance causes the coin to come to rest.

Common Misconceptions:

Students will think that the stack of coins will knock down.

Photographs and Movies

Quarter Karate

Put all photos in the class Picasa Album and reference here. 

Additional Information/References

           Nickel Karate - Instructions

           Information about Inertia