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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
The pulley system has drawn lifts a load of 150 N when an effort of 60 N is applied. Find its mechanical advantage.
Explain how a gear system can be used to obtain gain in speed? Given one example.
Give two reasons why the efficiency of a single movable pulley system is not 100%.
Give reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
The diagram below shows a pulley arrangement.
(i) In the diagram, mark the direction of the forces due to tension, acting on the pulley P.
(ii) What is the purpose of the pulley Q?
(iii) If the tension is T newton, deduce the relation between T and E.
(iv) Calculate the velocity ratio of the arrangement.
(v) Assuming that the efficiency of the system is 100%, what is the mechanical advantage?
(vi) Calculate the value of E
Give a reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
(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?
What is a pulley?
Draw a diagram showing a block and tackle system of 4 pulleys.
(i) State, how many strands of tackle support the load?
(ii) Draw arrows to represent tension in each strand.
(iii) Find the mechanical advantage of the system, stating the assumptions made.
(iv) If the load is pulled up by a distance 1m, how much does the effort end move?
A pulley is a machine made up of a ______.
