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Meera chose to use a block and tackle system of '9' pulleys instead of a single movable pulley to lift a heavy load. Why should she connect more number of pulleys in the upper fixed block? - Physics

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Question

Meera chose to use a block and tackle system of '9' pulleys instead of a single movable pulley to lift a heavy load.

Why should she connect more number of pulleys in the upper fixed block?

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Solution

In the upper fixed block, she adds extra pulleys to increase the mechanical advantage.

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The diagram below shows a pulley arrangement.

(i) In the diagram, mark the direction of the forces due to tension, acting on the pulley P.

(ii) What is the purpose of the pulley Q?

(iii) If the tension is T newton, deduce the relation between T and E.

(iv) Calculate the velocity ratio of the arrangement.

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(a)  Fig represents an incomplete diagram of a simple string pulley      system. Copy this diagram on a new page and complete it and mark where the effort must be applied to lift the load.
(b) What is the velocity ratio of this system?
(c) If the pulley system is 80% efficient and the load is 720 N, then
    (i) What effort must be applied to lift the load?
    (ii) What work must be done must be done in lifting the load through   a distance of 2 m using this machine?


What is a block and tackle system of pulleys? What precautions would you observe while rounding the string so that the effort is applied in the downward direction?


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