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प्रश्न
What is the relation between the mechanical advantage and the number of strands of string used to support the load, in a ‘block and tackle’ set-up?
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उत्तर
The mechanical advantage is equal to the number of strands of string, used to support the load, only if the ‘block and tackle set up’ can be assumed to be ideal (absence of friction, etc.) and the lower blocks of pulleys have negligible weight. Both these conditions cannot be satisfied in actual practice. Hence, in practical situations, the M.A. of a ‘block and tackle set up’ is always less than the fire number of strands of string used to support the load.
संबंधित प्रश्न
What is a gear system ?
Define the following term in reference to a gear system of Driving gear ?
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)?
Draw a diagram of a combination of three movable pulleys and one fixed pulley to lift up a load. In the diagram, show the directions of load, effort and tension in each strand. Find:
- mechanical advantage,
- Velocity ratio and
- efficiency of the combination in ideal situation.
In the case of a block and tackle arrangement, the mechanical advantage increases with the number of pulleys. Explain.
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?
Draw a diagram of a single fixed pulley and obtain expressions for its:
(i) Mechanical advantage,
(ii) Velocity ratio, and
(iii) Efficiency, in the ideal case.
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 |
A pulley is a machine made up of a ______.
State one advantage of single movable pulley.
