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प्रश्न
Give reason for the following:
The lower block of a block and tackle pulley system must be of negligible weight
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उत्तर
The lower block pulleys should be as light as possible to maximise efficiency, and lubricants should be used to reduce friction in pulley bearings.
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संबंधित प्रश्न
Select the correct alternative:
A pulley is used because of it
State two functions of a machine.
Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
Define the following term in reference to a gear system for Gear ratio ?
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)?
Name the type of single pulley that can act as a force multiplier. Draw a labeled diagram of the pulley mentioned by you.
Write two uses of pulleys. Is pulley a force multiplier?
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?
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?
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.
