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In this programme, film and studio demonstrations are used to illustrate mechanics in action. The concepts of momentum, force and the addition of forces to give a resultant in another direction explained by using examples from the real world. The programme then forms an ideal complement to the course unit both in understanding by seeing and reinforcing mathematical techniques such as vector addition of velocities, forces etc. Film of different impacts illustrates the extreme force-time curves. A freeze frame technique is used of a boxer punching a punch bag in slow motion to analyse the exchange of momentum between punch and bag and the exchange of kinetic energy to potential energy of the bag. A studio demonstration of a Pelton wheel using stroboscopic photography show the operation of this simple prime mover. Its use for generation of electricity is discussed and the efficiency of a Pelton bucket versus flate plate runner is demonstrated. An omni-directional tractor shows a real application of the addition of velocities according to the triangle rule. The idea of a balance of forces on a yacht sailing into the wind is shown to be another example of the triangle rule in action, this time for forces.
Metadata describing this Open University video programme
Module code and title: T100, The man-made world: a foundation course
Item code: T100; 06
First transmission date: 20-02-1972
Published: 1972
Rights Statement:
Restrictions on use:
Duration: 00:22:07
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Producer: Tony Jolly
Contributors: Keith Attenborough; Geoffrey Holister
Publisher: BBC Open University
Keyword(s): Electric generation; Force; Impact experiments; Momentum; Omni-directional tractor; Pelton wheel; Triangle rule; Vector addition; Yacht analogy
Footage description: The principle of "Force = Rate of change of momentum" is examined. Shot of car crashing into barrier. Shot of RAF Lightning jet braking in a gravel barrier. Shot of car crashing into pavement after falling from roof of building. The above shots all illustrate a rate of change of momentum. (force) Still shots of various objects in a state of change of momentum. Time/Force curve is shown for 1. Impact of a bullet. 2. Impact of duck landing on ice. 3. Boxer hitting a punching bag. Large number of impacts in rapid succession result in a uniform Time/Force curve. Shots of a Pelton Wheel being turned by water force. Models of the Pelton Wheel and of one of its buckets are used to explain the principle of its operation. R.P.M.s of the Pelton Wheel are monitored with a tachometer. Shot of a greatly enlarged photo of a Pelton Wheel in operation. Photo is used as an aid in discussing the action of the wheel. Shot of diagrams of a Pelton Wheel bucket and of a flat plate are used to illustrate the superior efficiency of the bucket. A Pelton Wheel with flat blades rather than buckets is rigged up. Diagram of an electric power station station shows how Pelton Wheels are used. Short film shows the construction of a large Pelton Wheel. Buckets are hand ground. Film shows the installation of the wheel at a hydroelectric power site. Shots of a Pelton Wheel with flat blades being rotated by water pressure. The efficiency is markedly lower than with buckets. (R.P.M. monitored with tachometer). A four tracked tractor (with felt pen attached) is used to demonstrate the rule : "Vectors add by the triangle". The tractor moves in one direction, than at right angles and finally diagonally to form a triangle. Shots of sailboat tacking into the wind. This is a further demonstration of the 'Vectors add by the triangle' rule. Diagram of a small sailboat is used to illustrate the aerofoil properties of the sail. Model of an actual aerofoil is subjected to wind force. Further diagrams and models of sailboats illustrate tacking and the 'Vectors add by the triangle' rule.
Master spool number: 6LT/70293
Production number: 00521_2522
Videofinder number: 2150
Available to public: no