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प्रश्न
Give reason for the following:
The efficiency of a pulley is always less than 100%
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उत्तर
The two reasons are:
(a) Some effort is wasted and overcoming the friction between the strings and the grooves of the pulley.
(b) Some effort is wasted in lifting up the movable block along with the load.
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संबंधित प्रश्न
What is the mechanical advantage of an ideal pulley?
Explain how a gear system can be used to obtain gain in torque? Given one example.
The diagram below shows a pulley arrangement.
- Name the pulleys A and B.
- In the diagram, mark the direction of tension on each strand of string.
- What is the purpose of the pulley B?
- If the tension is T, deduce the relation between
- T and E, and
- E and L.
- What is the velocity ratio of the arrangement?
- Assuming that the efficiency of the system is 100%, what is the mechanical advantage?
A block and tackle pulley system has a velocity ratio 5. Draw a labelled diagram of this system. In your diagram, indicate clearly the points of application and the directions of the load and effort.
What is a block and tackle system of pulleys?
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?
Draw the diagram of a single movable pulley and obtain its mechanical advantage, velocity ratio, and efficiency.
Draw a diagram of a single fixed pulley and obtain expressions for its:
(i) Mechanical advantage,
(ii) Velocity ratio, and
(iii) Efficiency, in the ideal case.
If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.
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.
