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प्रश्न
Give two reasons why the efficiency of a single movable pulley system is not 100%.
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उत्तर
The efficiency of a single movable pulley system is not 100% this is because
- The friction of the pulley bearing is not zero.
- The weight of the pulley and string is not zero.
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संबंधित प्रश्न
State whether the following statement is True or False.
A pulley changes the direction of force.
Name a machine to change the direction of force ?
Explain the working of a gear system.
The diagram below shows a pulley arrangement :
(i) Copy the diagram and mark the direction of tension on each strand of the string.
(ii) What is the velocity ratio of the arrangement ?
(iii) If the tension acting on the string is T, then what is the relationship between T and effort E ?
(iv) If the free end of the string moves through distance x, find the distance by which the load is raised.
Give reason for the following:
The efficiency of a pulley is always less than 100%
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?
What is a block and tackle system of pulleys? What precautions would you observe while rounding the string so that the effort is applied in the downward direction?
Diagram given below shows an arrangement of four pulleys. A load L is attached to the movable lower block and effort E is applied at the free end of the string.
Copy the diagram; and
(i) Draw arrows to indicate tension in each part of the string; and
(ii) Calculate the mechanical advantage of 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.
State one advantage of single movable pulley.
