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प्रश्न
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?
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उत्तर
If there are n movable pulleys connected to a fixed pulley, then the velocity ratio is
V.R = 2n
Velocity ratio of the system = 2.
Mechanical Advantage = `"Load"/"Effort"=1000/600`
=`5/3`
Efficiency = `"M.A."/"V.R."`
= `(5//3)/2=5/(3xx2)=5/6`
= 83.3%.
संबंधित प्रश्न
A pulley system with VR = 4 is used to lift a load of 175 kgf through a vertical height of 15 m. The effort required is 50 kgf in the downward direction. (g = 10 N kg-1)
Calculate:
- Distance moved by the effort
- Work done by the effort
- M.A. of the pulley system
- Efficiency of the pulley system
Is the above pulley system an ideal machine or not?
Explain how a gear system can be used to obtain gain in speed? Given one example.
Explain how a gear system can be used to obtain gain in torque? Given one example.
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)?
Give reason for the following:
In case of a block and tackle arrangement, the mechanical advantage increases with the increase in the number of pulleys.
Give a reason for the following:
In a single fixed pulley, the velocity ratio is always more than the mechanical advantage.
Write two uses of pulleys. Is pulley a force multiplier?
What is a pulley?
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.
