Advertisements
Advertisements
प्रश्न
If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.
Advertisements
उत्तर
If the weight of the movable pulley with its frame is W, in equilibrium
E = T
L + W = 2T
Or L + W = 2E
⇒ L = 2E − W
MA =`"L"/"E"=("2E"-"W")/"E"=2-"W"/"E"`
VR will remain same, h = `"MA"/"VR"`
`=(2-"W"/"E")/2=1-"W"/(2"E")`
If W << 2E, then 2E = L
Or h = `(1-"W"/"L").`
संबंधित प्रश्न
Fill in the blank:
A pulley is used to change ........................
State two functions of a machine.
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 ascending a hill ?
Write two uses of pulleys. Is pulley a force multiplier?
(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?
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.
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 |
State one advantage of single movable pulley.
A block and tackle system of pulleys has a velocity ratio of 4.
- Draw a labelled diagram of the system indicating clearly the direction of the load and effort.
- Calculate the potential energy of the load 100 kgf lifted by this pulley to a height 5 m. (g = 10 ms−2)
