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प्रश्न
(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?
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उत्तर
a) Corrert wínding ofrope around pulleys, load and effortis as shown
b) Since there are four strings in the block and tackle system, therefore, the velocíty ratio ofthe systemís V.R = n = 4
c)
(i) Given load L = 720 N
Let effort = E
Efficiency = `"M.A"/"V.R"`
or, 80% = `"L/E"/4`
or, `80/100 xx 4 = 720/E`
or, E = `(720 xx 100)/(80 xx 4)` = 225 N
(ii) Given, Load L = 720 N
Displacement - of - load, dL = 2m
Efficiency = `"work - output"/"work - input"`
or work - input = `"work - output"/"efficiency" = ("Load" xx "d"_"L")/"n"`
or, Work - input = `(720 xx 2)/0.8` = 1800 J
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संबंधित प्रश्न
Define the following term in reference to a gear system for Gear ratio ?
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.
Give 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 3. Draw a diagram showing the point of application and direction of load (L), effort (E) and tension (T). It lifts a load of 150 N by an effort of 60 N. Calculate its mechanical advantage. Is the pulley system ideal? Give reason.
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
What is a block and tackle system of pulleys?
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.
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.
_______ is a machine made up of wheel and rope.
A pulley is a machine made up of a ______.
