053 – Inertia of mass

Consequences of the inertia of mass

Introduction to:  

Inertia, torque, static friction, conservation of momentum.  

Material:  

  • small box (e.g., matchbox).   
  • sheet of paper  

Instructions:    

Place the box with the smallest side surface on the edge of the paper. This will allow three different experiments to be performed:  

  1. Pull moderately fast, but abruptly, on the paper.  
  2. Pull on the paper while slowly accelerating. Then stop suddenly.  
  3. Pull the paper away from under the box with a jerk. 

Observation:  

The box ….  

  1.     … falls over backwards  
  2.     … falls over to the front 
  3.     … remains standing  

Didactic Potential:  

The different reactions of the box to different types of movement of the support demonstrate the inertia of the mass of the box, its static friction on the support, and the torque created when the support is pulled away.  

Tips:  

  • Bend the paper slightly upwards at the opposite end to make it easier to grip.  
  • The box can be weighted down by filling it with sand.