Beating Gravity

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In this demonstration, learners watch as a device drops a ball into a cup without touching the ball or cup, even though the ball and cup are virtually side-by-side. Specifically, this device demonstrates gravitational acceleration and center of percussion. This resource includes instructions on how to build the device, which learners can construct with adult supervision.

Quick Guide

Preparation Time:
1 to 2 hours

Learning Time:
5 to 10 minutes

Estimated Materials Cost:
$10 - $20 per group of students

Age Range:
Ages 11 - 18

Resource Types:
Activity, Demonstration, Lesson/Lesson Plan


Materials List (per group of students)

  • Golf tee
  • Golf ball or other hard small ball
  • 2 1x4 cut to the same length of about 3.2 ft (about a meter)
  • 1 piece of wood roughly 3/4 in. by 2.5 ft. (the stick)
  • Plastic cup or other small container
  • Door hinge
  • Screws for hinge
  • Sponge, tissue, or other material to soften the fall of the ball
  • Fishing nail or pin


  • Physical Sciences
    • Motion and Forces
      • Gravity
      • Acceleration
      • Center of Gravity
    • States of Matter
      • Liquids
    • Structure and Properties of Matter
      • Mass and Weight
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations


To use this activity, learners need to:

  • see

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access


  • Muller, Eric


  • All rights reserved, Exploratorium, 2005