Advertisements
Advertisements
प्रश्न
Give reason for the following:
The efficiency of a pulley is always less than 100%
Advertisements
उत्तर
The two reasons are:
(a) Some effort is wasted and overcoming the friction between the strings and the grooves of the pulley.
(b) Some effort is wasted in lifting up the movable block along with the load.
APPEARS IN
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
Define the following term in reference to a gear system for Driven gear ?
Define the following term in reference to a gear system for Gain in torque ?
Give two reasons why the efficiency of a single movable pulley system is not 100%.
Give reason for the following:
The lower block of a block and tackle pulley system must be of negligible weight
The diagram below shows a pulley arrangement :
(i) Copy the diagram and mark the direction of tension on each strand of the string.
(ii) What is the velocity ratio of the arrangement ?
(iii) If the tension acting on the string is T, then what is the relationship between T and effort E ?
(iv) If the free end of the string moves through distance x, find the distance by which the load is raised.
(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?
In the case of a block and tackle arrangement, the mechanical advantage increases with the number of pulleys. Explain.
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.
Draw the diagram of a single movable pulley and obtain its mechanical advantage, velocity ratio, and efficiency.
