Topic Content:
- Pulley System
- Inclined Plane
- Wedge
- Screw Jack
- Wheel and Axle
- Gears
Pulley System:
A pulley is a fixed wheel hung on a suitable support with a rope passing round its groove. They are commonly used in construction sites to lift or lower heavy loads.
The velocity ratio of a pulley system is always equal to the number of pulleys in the system.
For a block and tackle system, each block contains one or more pulleys mounted side by side on the same axle and runs independently. A single rope is passed through each pulley and they are commonly used in cranes and lifts.
Since the Velocity Ratio V.R of a pulley system is generally equal to the number of pulleys, for the system with 5 pulleys V.R = 5, similarly, for the system with 4 pulleys V.R = 4.
As the number of pulleys increases so does the Mechanical advantage M.A. If the efficiency of the system is 100%, then the V.R = M.A
Example 1.3.1:
A block and tackle system has a velocity ratio of 4 and is used to raise a load of mass 50 kg. If the efficiency of the system is 75%, determine the minimum effort required to raise the load (g = 10ms-2).
Solution
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