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प्रश्न
State two reasons, why the efficiency of a pulley system is not 100 percent?
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उत्तर
The two reasons are:
(i) Some effort is used (or wasted) in overcoming the friction between the string and the grooves of the pulleys.
(ii) Some effort is used up (wasted) in lifting up the movable block along with the load.
On account of the above two reasons, effort applied is always more than the load lifted up and so the M.A. is always less than 1. Hence efficiency is always less than 100%.
संबंधित प्रश्न
A block and tackle system has V.R. = 5.
Rohan exerts a pull of 150 kgf. What is the maximum load he can raise with this pulley system if its efficiency = 75%?
Fill in the blank:
A pulley is used to change ........................
Select the correct alternative:
A pulley is used because of it
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.
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 a block and tackle system of pulleys?
Give a reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
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.
| Meera chose to use a block and tackle system of '9' pulleys instead of a single movable pulley to lift a heavy load. |
Why should she connect more number of pulleys in the upper fixed block?
