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प्रश्न
State two reasons, why the efficiency of a pulley system is not 100 percent?
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उत्तर
The two reasons are:
(i) Some effort is used (or wasted) in overcoming the friction between the string and the grooves of the pulleys.
(ii) Some effort is used up (wasted) in lifting up the movable block along with the load.
On account of the above two reasons, effort applied is always more than the load lifted up and so the M.A. is always less than 1. Hence efficiency is always less than 100%.
संबंधित प्रश्न
Fill in the blank:
A pulley is used to change ........................
Give two reasons why the efficiency of a single movable pulley system is not 100%.
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)?
What is a block and tackle system of pulleys?
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.
Write two uses of pulleys. Is pulley a force multiplier?
In the alongside the figure of two pulleys shown a system in which one pulley is fixed and the other is movable. What is the velocity ratio of the system?
An effort of 600 N is needed to lift a weight of 1000 N. What are the mechanical advantage and efficiency of the pulley system?
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?
Diagram given below shows an arrangement of four pulleys. A load L is attached to the movable lower block and effort E is applied at the free end of the string.
Copy the diagram; and
(i) Draw arrows to indicate tension in each part of the string; and
(ii) Calculate the mechanical advantage of the system.
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.
