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प्रश्न
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?
उत्तर
The mechanical advantage is equal to the number of strands of string, used to support the load, only if the ‘block and tackle set up’ can be assumed to be ideal (absence of friction, etc.) and the lower blocks of pulleys have negligible weight. Both these conditions cannot be satisfied in actual practice. Hence, in practical situations, the M.A. of a ‘block and tackle set up’ is always less than the fire number of strands of string used to support the load.
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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 with VR = 4 is used to lift a load of 175 kgf through a vertical height of 15 m. The effort required is 50 kgf in the downward direction.
(g = 10 N kg-1)
Calculate
1) Distance moved by the effort
2) Work done by the effort
3) M.A. of the pulley system
4) Efficiency of the pulley system
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 ?
In which direction does the force need to applied, when a single pulley is used with a mechanical advantage greater than one? How can you change the direction of force applied without altering its mechanical advantage? Draw a labelled diagram of the system.
What is the use of a fixed pulley?
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.
(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?
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.
_______ is a machine made up of wheel and rope.
