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प्रश्न
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.
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उत्तर
Given:
L = 40 kgf,
dL = 2m,
t = 5 s,
E = 48 Kgf.
(i) Mechanical advantage (M.A.) =`"L"/"E"=40/48=5/6=0.833`
(ii) If the effort moves a distance d downwards, the load also moves a distance d upwards. So velocity ratio (V.R.) = d/d = 1,
Efficiency = `"M.A."/"V.R."=0.833/1`
= 0.833 (or 83.3%).
The efficiency of the pulley is not 100% because some energy is wasted in overcoming the friction in the pulley bearings.
(iii) The energy gained by the load in 5s = Load × Displacement of load in 5s
= 40 kgf × 2m
= 80 kgf × m.
(iv) Power developed by the boy =`"Effort×Displacement of effort"/"Time"=(48"kgf"×2"m")/(5"s")`
= 19.2 kgf × ms−1.
संबंधित प्रश्न
A boy uses a single fixed pulley to lift a load of 50 kgf to some height. Another boy uses a single movable pulley to lift the same load to the same height. Compare the effort applied by them. Give a reason to support your answer.
Select the correct alternative:
A pulley is used because of it
Answer the following in detail.
How does a pulley make work simpler?
Explain the working of a gear system.
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 block and tackle system of pulleys?
Write two uses of pulleys. Is pulley a force multiplier?
The pulley system shown in the figure is to be used to lift a load W. If the man applying the effort cannot apply a force exceeding 1000 N, what is the maximum load that can be lifted?
The actual load that the man is finally able to lift turns out to be 2700 N. What are the values of the actual M.A., obtained, and the efficiency of the actual set-up?
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?
Name the type of single pulley that has an ideal mechanical advantage equal to 2. Draw a labelled diagram of the pulley mentioned by you.
