Four fifths of the length of the steel bar is sawed into small sections of the same length for 6 times, each section is () m long. If it takes 2 minutes to sawn into two sections, it takes 2 minutes to sawn into six sections () minutes Why?

Four fifths of the length of the steel bar is sawed into small sections of the same length for 6 times, each section is () m long. If it takes 2 minutes to sawn into two sections, it takes 2 minutes to sawn into six sections () minutes Why?

The first empty: four fifths (6 + 1) = four fifths of 35 meters
Second empty: 2 × (6-1) = 10 minutes

There is a 220kV overhead power line, using lgj-2 × 185 double bundle conductor. The calculated outer diameter of each conductor is 19mm. The three-phase conductors are arranged in unequal triangle. The distance between lines is D12 = 9m, D23 = 8.5m, D13 = 6.1m. The number of bundle conductors is n = 2, and the bundle spacing is d = 400mm. Try to find the parameters of the power line and make the equivalent circuit

It is also called double bundle conductor. The conductor is ACSR, in which the comprehensive cross-sectional area of the aluminum wire is 400 square mm. The latter means that the overhead ground wire of the line adopts good conductor, and the ground wire 0 is aluminum clad steel strand, and the overall comprehensive cross-sectional area is 120 square mm

Machinery is not allowed to operate close to overhead transmission line. How many meters is the safe distance between machinery operation and 220 kV overhead transmission line in vertical direction?

The vertical direction shall not be less than 4 meters. For example, the bridge erecting machine of highway or railway needs to reasonably increase the safety margin (mainly design error + construction error + uncertain factors + special conditions such as disconnection during operation), At the same time, combined with the reasonable control margin of the crossing gear, that is: the top elevation of mechanical operation + margin (0.5 + 0.7 + 0.3 + 1) is relatively safe. If it is allowed to take 7m, it is the best. This problem should be based on a fixed position to analyze the size of these error factors, and reasonable value, the above is the thinking reference