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प्रश्न
There is no gain in mechanical advantage in the case of a single fixed pulley. Explain, why the pulley is then used?
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उत्तर
It is used only to change the direction of effort to a more convenient direction and to use one’s own weight for the effort.
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संबंधित प्रश्न
The mechanical advantage of an actual pulley is less than one. Give a reason. What is the justification for using the pulley then?
Differentiate between a single fixed pulley and a single movable pulley.
What should be the gear ration of a car : equal to 1, less than 1 or greater than 1, while gaining speed on the road ?
What is a single movable pulley? What is its mechanical advantage in the ideal case?
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.
(v) Assuming that the efficiency of the system is 100%, what is the mechanical advantage?
(vi) Calculate the value of E
A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage. For what purpose is such a pulley used?
What is the relation between the mechanical advantage and the number of strands of string used to support the load, in a ‘block and tackle’ set-up?
A pulley system has a velocity ratio of 4 and an efficiency of 90%. Calculate:
(i) the mechanical advantage of the system.
(ii) the effort required to raise a load of 300 N by the system.
A boy lifts a load of 40 kgf through a vertical height of 2m in 5s by using a single fixed pulley when he applies an effort of 48 kgf. Calculate:
(i) the mechanical advantage, and
(ii) the efficiency of the pulley. Why is the efficiency of the pulley is not 100%?
(iii) the energy gained by the load in 5s, and
(iv) the power developed by the boy in raising the load.
Complete the table.
| S. No | Types of Simple Machine | Example |
| 1. | Pulley | |
| 2. | Wheel and axle | |
| 3. | Wedge | |
| 4. | Inclined plan | |
| 5. | Lever | |
| 6. | Screw |
