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Question
Give two reasons why the efficiency of a single movable pulley system is not 100%.
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Solution
The efficiency of a single movable pulley system is not 100% this is because
- The friction of the pulley bearing is not zero.
- The weight of the pulley and string is not zero.
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RELATED QUESTIONS
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
Fill in the blank:
A pulley is used to change ........................
Answer the following in detail.
How does a pulley make work simpler?
What is a single movable pulley? What is its mechanical advantage in the ideal case?
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) Copy the diagram and mark the direction of tension on each strand of the string.
(ii) What is the velocity ratio of the arrangement ?
(iii) If the tension acting on the string is T, then what is the relationship between T and effort E ?
(iv) If the free end of the string moves through distance x, find the distance by which the load is raised.
Give a reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
Write two uses of pulleys. Is pulley a force multiplier?
A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage. Name the type of pulley used.
If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.
