1R40.10 Sandbag and Tennis Ball


Elastic and inelastic collisions, coefficient of restitution, conservation of linear momentum


A sand-filled balloon and a tennis ball are individually attached to an aluminum rod, that is fixed on a lab stand, by strings. When the two objects are pulled away and released simultaneously, each object will hit a stationary wooden block placed in the object's line of motion. The collision between sandbag and wooden block is an inelastic one and the wooden block will not topple over after collision. On the other hand, the collision between tennis ball and wooden block is nearly elastic. Thus, the wooden block will be knocked down.



  • [1] Lab stand
  • [3] 90-degree clamp
  • [3] Aluminum rod
  • [1] Sand-filled balloon
  • [1] Tennis ball
  • [2] Bulldog clip
  • [2] Wooden block
  • [2] String 

Classroom Assembly

  1. Place the lab stand on a horizontal surface.
  2. Attach a bar on which to hang the sandbag and ball.
  3. Attach sandbag and tennis ball to the bar by strings. Clip the strings in place.
  4. Attach a bar to mark starting position of the objects.
  5. Let the two objects to hang vertically at equilibrium position.
  6. Place a wooden block next to each object.
  7. Test the apparatus and adjust the starting position bar as required.


  1. Pull the two objects away from the wooden blocks until both objects touch the rod.
  2. Release the two objects simultaneously.
  3. Observe that only one block topples over after a collision with the object.


Additional Resources


  • PIRA 1R40.10


  • Don't attempt this at home!

Last revised

  • 2017


Related AV

Related demos

  • Dead and live balls


If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.