Projectile Motion
Forces and Motion

Water jet through rings

Practical Activity for 14-16 PRACTICAL PHYISCS


This experiment shows a stream of water following a parabolic path. It is really impressive to see the water still passing through the hoops even when the rod is tilted.

Apparatus and Materials

  • Glass tube drawn to a jet
  • Wood pole or beam, rigid, at least 2cm long
  • Rings, 3, 10 - 12cm diameter
  • Constant head of pressure apparatus
  • Retort stands, bosses and clamps, 2 (one very tall)
  • Bucket
  • Panel pins
  • Rubber tubing
  • Thread and rubber bands

Health & Safety and Technical Notes

When setting up the constant head tank it will be necessary to take care: use a step ladder rather than climbing on the bench, and have an assistant present to pass things.

Read our standard health & safety guidance

Strap the glass jet securely to one end of the pole or beam so that water emerging from the jet will do so in a direction parallel to the length of the pole.

At equal distances from the end of the jet, hammer pairs of panel pins into the pole or beam as shown.

These pins serve to support the rings by bifilar threads whose lengths between the levels indicated are 15 cm, 60 cm and 135 cm.


  1. Mount the beam horizontally near to a sink and connect the jet to the constant pressure head high above the bench.
  2. Turn on the water and adjust its flow rate until a jet of water passes through each of the rings on its way to the sink or bucket.
  3. Tilt the whole device to other angles, showing that the water stream will continue to pass through the rings.

Teaching Notes

  • The pole acts as a tangent to the motion of the water at the jet at its beginning. From that pole the water falls away from its original straight path by the same amount in a given time whatever the tilt. The initial velocity of the water has a horizontal and vertical component; the horizontal component remains unchanged and is independent of the changes in vertical velocity due to gravity.
  • This experiment could be used in preparation for:

    The apple and arrow experiment

This experiment was safety-tested in April 2005

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