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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 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:
- Distance moved by the effort
- Work done by the effort
- M.A. of the pulley system
- Efficiency of the pulley system
The pulley system has drawn lifts a load of 150 N when an effort of 60 N is applied. Find its mechanical advantage.
Is the above pulley system an ideal machine or not?
Differentiate between a single fixed pulley and a single movable pulley.
What is a single movable pulley? What is its mechanical advantage in the ideal case?
The diagram below shows an arrangement of three pulleys A, B, and C. The load is marked as L and the effort as E.
- Name the Pulleys A, B, and C.
- Mark in the diagram the directions of load (L), effort (E) and tension T1 and T2 in the two strings.
- How are the magnitudes of L and E related to the tension T1?
- Calculate the mechanical advantage and velocity ratio of the arrangement.
- What assumptions have you made in parts (c) and (d)?
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.
The mechanical advantage of an ideal single movable pulley is ______.
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?
