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प्रश्न
The alongside figure shows the combination of a movable pulley P1 with a fixed pulley P2 used for lifting up a load W.
(i) State the function of the fixed pulley P2.
(ii) If the free end of the string moves through a distance x, find the distance by which the load W is raised.
(iii) Calculate the force to be applied at C to just raise the load W = 20 kgf, neglecting the weight of the pulley P1 and friction.
उत्तर
(i) It is quite difficult to apply effort in the upward direction if no fixed pulley P2 is used. The fixed pulley changes the direction of effort from upwards to downwards, making the application of the effort more convenient and easier.
(ii) As the movable pulley doubles the effort,
∴ Force, L = 2T
i.e., W = 2T
Mechanical advantage M.A. =`(2"T")/"T"=2`
and V.R. =`("Distance travelled by effort")/("Distance travelled by load")=(2"x")/"x"=2`
The distance travelled by load is half the distance moved by effort = x / 2.
(iii) Since W = 2T or 20 kgf = 2T Here, T = effort
∴ Effort applied =`20/2` = 10 kgf.
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संबंधित प्रश्न
Answer the following in detail.
How does a pulley make work simpler?
What should be the gear ration of a car : equal to 1, less than 1 or greater than 1, while gaining speed on the road ?
Differentiate between a single fixed pulley and a single movable pulley.
What is the use of a fixed pulley?
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
Name a machine which is used to:
change the direction of force applied.
(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?
There is no gain in mechanical advantage in the case of a single fixed pulley. Explain, why the pulley is then used?
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?
Complete the table.
| S. No | Types of Simple Machine | Example |
| 1. | Pulley | |
| 2. | Wheel and axle | |
| 3. | Wedge | |
| 4. | Inclined plan | |
| 5. | Lever | |
| 6. | Screw |
