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प्रश्न
Draw a diagram of a single fixed pulley and obtain expressions for its:
(i) Mechanical advantage,
(ii) Velocity ratio, and
(iii) Efficiency, in the ideal case.
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उत्तर
The diagram of a single fixed pulley is shown alongside. If T is the tension in each strand of the string and in the ideal case string is massless and there is no friction in the pulley bearings, then in equilibrium, E = T and L = T
(i) Mechanical advantage = `"L"/"E"="T"/"T"=1`
(ii) If the effort E moves a distance d downwards, the load L moves the same distance d upwards.
So, velocity ratio = `"d"_"E"/"d"_"L"="d"/"d"=1`
(iii) Efficiency =`"M.A."/"V.R."=1/1` = 1 (or 100%).
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संबंधित प्रश्न
What is the mechanical advantage of an ideal pulley?
What is a gear system ?
What should be the gear ration of a car : equal to 1, less than 1 or greater than 1, while ascending a hill ?
The diagram below shows a pulley arrangement.
- Name the pulleys A and B.
- In the diagram, mark the direction of tension on each strand of string.
- What is the purpose of the pulley B?
- If the tension is T, deduce the relation between
- T and E, and
- E and L.
- What is the velocity ratio of the arrangement?
- Assuming that the efficiency of the system is 100%, what is the mechanical advantage?
The diagram below shows an arrangement of three pulleys A, B, and C. The load is marked as L and the effort as E.
- Name the Pulleys A, B, and C.
- Mark in the diagram the directions of load (L), effort (E) and tension T1 and T2 in the two strings.
- How are the magnitudes of L and E related to the tension T1?
- Calculate the mechanical advantage and velocity ratio of the arrangement.
- What assumptions have you made in parts (c) and (d)?
Draw a diagram of a combination of three movable pulleys and one fixed pulley to lift up a load. In the diagram, show the directions of load, effort and tension in each strand. Find:
- mechanical advantage,
- Velocity ratio and
- efficiency of the combination in ideal situation.
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The lower block of a block and tackle pulley system must be of negligible weight
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A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage. Name the type of pulley used.
