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प्रश्न
Draw the diagram of a single movable pulley and obtain its mechanical advantage, velocity ratio, and efficiency.
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उत्तर
Since it is inconvenient to apply the effort in an upward direction, a single fixed pulley is used to change the direction of effort.
In equilibrium, L = T + T = 2T
E = T
Mechanical advantage =`"Load(L)"/"Effort(E)"=(2"T")/"T"=2`
As the effort is pulled down through a distance dE, the two segments of the thread carrying the movable pulley and the load goes up by dE/2.
Hence, dL = dE/2
Velocity ratio (VR) = `"d"_"E"/"d"_"L"`
= `"d"_"E"/("d"_"E"/2)`
= 2.
Efficiency =`"MA"/"VR"`
= `2/2`
= 1 or 100%.
संबंधित प्रश्न
A block and tackle system has V.R. = 5.
Draw a neat labeled diagram of a system indicating the direction of its load and effort.
State two functions of a machine.
The mechanical advantage of an actual pulley is less than one. Give a reason. What is the justification for using the pulley then?
What should be the gear ration of a car : equal to 1, less than 1 or greater than 1, while gaining speed on the road ?
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 a single movable pulley? What is its mechanical advantage in the ideal case?
Differentiate between a single fixed pulley and a single movable pulley.
Give reason for the following:
In case of a block and tackle arrangement, the mechanical advantage increases with the increase in the number of pulleys.
What is a block and tackle system of pulleys?
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.
