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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 boy uses a single fixed pulley to lift a load of 50 kgf to some height. Another boy uses a single movable pulley to lift the same load to the same height. Compare the effort applied by them. Give a reason to support your answer.
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.
State two functions of a machine.
Differentiate between a single fixed pulley and a single movable pulley.
Name the type of single pulley that can act as a force multiplier. Draw a labelled diagram of the pulley mentioned by you.
Differentiate between a single fixed pulley and a single movable pulley.
What is a block and tackle system of pulleys?
Give a reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
Fig shown a block and tackles system of pulleys used to lift a load.
(i) How many strands of tackle are supporting the load?
(ii) Draw arrows to represent tension in each stand.
(iii) What is the mechanical advantage of the system?
(iv) When load is pulled up by a distance 1 m how far does the effort end move?
(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?
