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प्रश्न
The mechanical advantage of an actual pulley is less than one. Give a reason. What is the justification for using the pulley then?
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उत्तर
In an actual pulley due to friction, the mechanical advantage is less than 1 (i.e. the effort is more than the load).
The reason for using the pulley when its mechanical advantage is equal to 1 or less than 1 is that the pulley allows us to apply the effort downwards i.e. in a convenient direction. To raise a load directly upwards is difficult. But with the help of a pulley, the effort can be applied in the downward direction to move the load upwards. One can hang on it to make use of his own weight also in order to apply the effort.
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संबंधित प्रश्न
A pulley system has three pulleys. A load of 120 N is overcome by applying an effort of 50N. Calculate the Mechanical Advantage and Efficiency of this system.
Rohan exerts a pull of 150 kgf. What is the maximum load he can raise with this pulley system if its efficiency = 75%?
Give reason for the following:
In case of a block and tackle arrangement, the mechanical advantage increases with the increase in the number of pulleys.
Give reason for the following:
The lower block of a block and tackle pulley system must be of negligible weight
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. Name the type of pulley used.
A block and tackle system of pulleys has a velocity ratio of 4.
- Draw a labelled diagram of the system indicating clearly the points of application and directions of load and effort.
- What is the value of the mechanical advantage of the given pulley system if it is an ideal pulley system?
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.
Name the type of single pulley that has an ideal mechanical advantage equal to 2. Draw a labelled diagram of the pulley mentioned by you.
