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This programme is about angular momentum and the way it helps us understand physical systems. Milo Shott (OU) introduces the programme. A children's roundabout is set spinning. Whether viewed direc...tly, or through a mirror, it clearly has the same energy. So we need more than just energy to fully describe its motion. Ray Mackintosh (OU) reminds us that the same was true for linear motion, and led to the concept of linear momentum. So we introduce a new concept called angular momentum for our roundabout. Milo defines this for a single particle as the vector product r X p and shows using the right-hand rule how we discriminate clockwise from anticlockwise motion. Ray then extends the definitions to a large rotating cylinder, and derives the expression L=Iw, where I is the moment of inertia. He then shows that for a spinning cylinder, L is a conserved quantity, and states the law of conservation of angular momentum. Milo then introduces the concept of torque and relates it to change in angular momentum. Ray checks his argument using a "windmill" set spinning by a mass on a string. He sets students a problem based on his experiment to do after the programme. Milo summarizes and then shows us two examples of conservation of angular momentum from real life: a dog shaking off water, and a cat freely falling onto a table. Ray looks at an example in Skylab where conservation of angular momentum and energy enable us to understand the notions of a drinking bottle: and, Milo concludes the programme by discussing conservation in the Earth Moon rotating system.
Metadata describing this Open University video programme
Module code and title: S271, Discovering physics
Item code: S271; 04
First transmission date: 31-03-1982
Published: 1982
Rights Statement:
Restrictions on use:
Duration: 00:25:00
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Producer: Nick Brenton
Contributors: Raymond Mackintosh; Milo Shott
Publisher: BBC Open University
Keyword(s): Angular; Cat falling; Dog shaking off water; Gyroscope; Momentum; Right-hand rule; Round-a-bout; Skylab; Space; Torque
Master spool number: HOU3840
Production number: FOUS228N
Videofinder number: 1783
Available to public: no