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प्रश्न
A ‘block and tackle’ system used 3 pulleys in the lower block and 4 pulleys in the upper block. What is the ‘velocity ratio’ of this system? If the load is to be lifted by a person capable of applying a maximum effort of 1000 N, what is the maximum load than can be lifted under ideal conditions?
The actual maximum load that gets lifted turns out to be 6300 N. What are the values of the actual M.A. and efficiency of the set-up?
उत्तर
There being 7 pulleys in all, the load is supported by 7 strands of string. Hence it gets lifted only through 1/7 th of the distance through which the effort is applied. Hence the velocity ratio of the setup has a value 7.
Under ideal conditions, M.A. = V.R. = 7
Hence, the maximum load that can be lifted under ideal conditions is:
Effort × 7 = 1000 N × 7 = 7000 N.
Under actual conditions, Load = 6300 N
and Effort = 1000 N
Hence, Actual M.A. =`(6300"N")/(1000"N")=6.3`
Also Efficiency =`"M.A."/"V.R."=6.3/7`
= 0.9 = 90%.
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संबंधित प्रश्न
Select the correct alternative:
A pulley is used because of it
The mechanical advantage of an actual pulley is less than one. Give a reason. What is the justification for using the pulley then?
Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
State if the following statement is true or false. Correct the statement if it is false.
A single movable pulley is a pulley that has its axis of rotation fixed.
Give two reasons why the efficiency of a single movable pulley system is not 100%.
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
Give reason for the following:
In case of a block and tackle system, the mechanical advantage increases with the increase in the number of pulleys.
State two reasons, why the efficiency of a pulley system is not 100 percent?
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?
