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प्रश्न
Give two reasons why the efficiency of a single movable pulley system is not 100%.
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
Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
Answer the following in short.
Explain the various functions that a machine can perform.
Solve the following numerical problem.
What effort will be required to lift a load of 500 N by a single movable pulley? [Hint: Mechanical advantage of a single movable pulley is two].
Name a machine to change the direction of force ?
The diagram below shows an arrangement of three pulleys A, B, and C. The load is marked as L and the effort as E.
- Name the Pulleys A, B, and C.
- Mark in the diagram the directions of load (L), effort (E) and tension T1 and T2 in the two strings.
- How are the magnitudes of L and E related to the tension T1?
- Calculate the mechanical advantage and velocity ratio of the arrangement.
- What assumptions have you made in parts (c) and (d)?
Give reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
Give reason for the following:
The lower block of a block and tackle pulley system must be of negligible weight
What is the use of a fixed pulley?
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 block and tackle system of pulleys has velocity ratio 4.
- Draw a labelled diagram of the system indicating clearly, the direction of the load and effort.
- Calculate the potential energy of the load 100 kgf lifted by this pulley to a height 5 m. (g = 10 ms-2)
