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Fluids and Viscosity
Liquids and their Properties
Be it the honey on our breakfast toast, the water from the tap or the air surrounding us – they all have one thing in common: in a physical sense they are fluids. That means: if you expose these substances to shear forces, their molecules are shifted against each other and the substance deforms continuously. With honey the shearing force of the knife on the one hand, and the resistance of the rough surface of the bread on the other, lead to this deformation – the honey is easy to spread. Fluids react to even slight force application. The deformation rate increases proportionally to the amount of shear stress. Therefore water flows faster from a plastic bottle when it is compressed more strongly. Physically speaking: the stronger the force, the faster the fluid is deformed. A solid, in contrast, offers a greater resistance to shear forces. Tension is built up inside it until eventually, above a certain threshold, deformation occurs – the stick breaks. But a solid can become a fluid if it changes its state of aggregation and melts. So the ice cube is no fluid, its melt water, however, is. It is easily deformed. It is almost the same with solid and molten steel. Thus temperature plays an important role in the behaviour of fluids.
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Curriculum-centred and oriented towards educational standards
Matching
Internet Addiction
The film consists of two parts. The first part is the 15-minute short film “In the Net”. It describes the problem of excessive Internet use in a humorous way, in particular the risk of losing touch with reality when chatting. The second part illustrates with three real persons how Internet addiction can develop and the problems encountered by those who are afflicted. The authentic statements are commented by an experienced therapist. For many pupils, the issues addressed here are related to their everyday lives. What is a “sensible” use of the Internet, where does pathological addiction start? In contrast to addiction to alcohol, nicotine or drugs, the public seems to be largely ignorant of the problem of this addiction, which is not related to any substance abuse. The film provides material for discussion in the classroom (crossdisciplinary) and can be used as a basis for the formulation of prevention strategies.