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प्रश्न
Give reason for the following:
The efficiency of a pulley is always less than 100%
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
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
Is the above pulley system an ideal machine or not?
What is a gear system ?
Define the following term in reference to a gear system for Gear ratio ?
What should be the gear ration of a car : equal to 1, less than 1 or greater than 1, while ascending a hill ?
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.
There is no gain in mechanical advantage in the case of a single fixed pulley. Explain, why the pulley is then used?
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.
State one advantage of single movable pulley.
