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प्रश्न
What is a block and tackle system of pulleys? What precautions would you observe while rounding the string so that the effort is applied in the downward direction?
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उत्तर
A block and tackle system of pulleys consists of two blocks of pulleys, each block having one or more than one pulleys. The upper block of pulleys is fixed to a rigid support and the lower block of pulleys is movable. The number of pulleys in the movable block is either equal or one less than the number of pulleys in the fixed block.
While rounding the string, its one end is attached to the hook of the movable block if the number of pulleys in the fixed block is more than that in the movable block or to the hook of the fixed block if the number of pulleys is the same in both the blocks.
संबंधित प्रश्न
Is the above pulley system an ideal machine or not?
What is a pulley?
Answer the following in short.
Explain the various functions that a machine can perform.
Differentiate between a single fixed pulley and a single movable pulley.
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 gaining speed on the road ?
Name a machine which is used to:
change the direction of force applied.
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.
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.
If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.
