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

Massive beam and anvil to show pressure exerted by a stream of balls

Demonstration

This is a larger, more dramatic version of Pressure exerted by a stream of balls.

Apparatus and materials

Anvil and beam

Marbles or 13 mm steel balls (not small steel balls)

Health & Safety and Technical notes


Eye protection must be worn. The teacher must stand on a step-ladder to release the balls, not on a stool or on a bench.

Construct a see-saw with a massive elastic anvil at one end. You can make a very good version by placing a sheet of about 13-mm Perspex on top of a massive steel block, with a thin layer of glycerine between them. Screw the Perspex into the steel near the edges. 

The anvil should be placed on a large wooden beam, which is pivoted near that end. The pivot could be a steel rod, fixed to the beam, free to roll on supports at the side. The other end of the beam must carry a counterweight and a pointer to indicate deflections. 
 
Place a large tray under the apparatus (or make a barrage around it) to catch the balls. (An inflatable paddling pool may be suitable.)

 

Procedure


Pour a stream of marbles or steel balls from as high as possible above the anvil and the see-saw shows there is a deflecting force on the beam.

 

Teaching notes


It helps if there is a release mechanism so the marbles or steel balls fall vertically onto the anvil. This is not an easy demonstration to set up but it is impressive when working. 

 
This experiment was safety-checked in March 2005