Four old school experiments, 1940

Temperature experiment: A Metal ball which is attached with a chain to metal a bar with bakelite handle. A metal plate with two circular holes also attached to metal a bar with bakelite handle. When the ball is cold it falls easily through the hole. After warming however no longer.

At the construction of railroads, at building bridges and houses, it is always taken into account the expansion of material. Because as something becomes warmer, it also becomes a little larger. The leidse professor Willem Jacob s Gravesande considered this device to show the impact to its students. In advance the ball is warmed up so that the ball no longer fitts through the ring. Then the ball is laid on the ring. When it cools down it fitts again through the ring. At that moment the ball falls suddenly down without someones help.  s Gravesande's intention was to surprise its students with this test so they wlould never forget the test. He succeeded in this as the ball and ring of 's Gravesande is still one of the most well known experiment.

Weights and forms experiment: A metal bar with a bracket and a wooden handle and four cubes: an iron (round and square), cork and lead.

Magnet: Magnet with the text. P. M. Tamson, instruments Den Haag.

Hollow and convex mirror.

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