Physics Dept. Demonstration Manual

DLD02 - Inertia, Stationary Sphere on Post


To illustrate the enertia of a body at rest.

  • Plastic sphere
  • Plastic card
  • Vertical rod, complete with base and horizontally acting spring


Place card on top of post. Place sphere on card. Pull back spring and release. The sphere stays on the post. (The friction between the card and the sphere is not sufficient to overcome the tendency of the sphere to maintain its original position, due to inertia).