Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds
 

Water jet through rings

Demonstration

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.

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.

Glass jet to end of 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. 

Hammered pins

Procedure


a Mount the beam horizontally near to a sink and connect the jet to the constant pressure head high above the bench. 

b 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. 

c Tilt the whole device to other angles, showing that the water stream will continue to pass through the rings. 

 

Teaching notes


1 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. 

2 This experiment could be used in preparation for the The 'apple and arrow' experiment
 
This experiment was safety-checked in April 2005

 

Related experiments


Testing projectile motion with a drawn parabola

The 'apple and arrow' experiment