Belt Loop Hanger

Learning Objectives

Students will investigate the importance of centre of mass with respect to balance.

Associated Curriculum Topic

Form and Function

Materials

  • cardboard (5’’x 10’’)
  • scissors
  • belt
  • glue sticks
  • University of Guelph belt loop template (see next page)

Introduction/Motivation

The centre of mass is a very important aspect to balance. When your centre of mass is no longer directly above your support (your feet), you are more likely to fall over. The stability of balancing toys (such as the one shown to the right) is built in by constructing them so that their centre of mass always remains below the support point. If the toys are tipped in any direction the center of mass is raised. This results in gravity exerting a restoring force which pulls it back towards an upright position.
In this activity, students will build their own balancing toy using our template. When the students first construct the hanger out of cardboard and try to balance the thin end on their finger, they will find that it is not stable. However, by placing a belt on the hanger, the centre of mass of the system is changed so that it is now below the support point, and a balanced structure results.

Procedure

  • using a pair of scissors, cut out the template and trace it on the piece of cardboard 3 times
  • cut each of the shapes on the cardboard
  • using a glue stick attach each of the cut outs together (while the glue dries you could talk about where students expect the center of mass of their object to be)
  • Once the glue is dry, try to balance the thinnest part of the structure on your index finger. Since the center of mass of the object is not directly above or below your index finger you should not be able to balance the belt loop hanger on your finger.
  • make a loop with a belt making sure that it will not come undone
  • loop the belt over the hanger and press it into the crease so that the belt buckle is at the furthest point away from the cardboard hanger
  • you should be able to balance the structure on your index finger since the centre of mass is now directly below your finger – try swinging the hanger on your finger and moving your hand around; you will find the configuration surprisingly stable

Investigating Questions

  • What is centre of mass?
  • Where is your centre of mass?
  • Where is the centre of mass of the cardboard structure?
  • Why does the belt make a difference? Where does it put the centre of mass?

Belt loop hanger template