Basic Electrical Installation Work

| Kategorie: Kniha  |

Strana 100 z 399

Jak získat tento dokument?






Poznámky redaktora
81m/s2 .81kW. The simplest form lever the crowbar, which useful because enables person lift load one end which greater than the effort applied through his her arm mus- cles the other end. Applying the principle turning forces lever, obtain the formula: Definition A lever any rigid body which piv- ots rotates about fixed axis or fulcrum. Calculate the rating (power) the motor the acceleration due gravity 9.Basic electrotechnical units and theory 89 Example 2 A hydroelectric power station pump motor working continuously during period raises 856tonnes water through vertical distance 60m. The mechanical advantage of a simple lever dependent upon the length lever either side the fulcrum. Power Mass Acceleration Distance moved Time taken W ) but Velocity Distance Time (m/s) Power Mass Acceleration Velocity Power m/s m/ 500 2 2 . this way the crowbar said provide ‘mechani- cal advantage’. Load force Distance from fulcrum Effort force Distance from fulcrum This formula can perhaps better understood referring Fig. lever any rigid body which pivots or rotates about fixed axis fulcrum.2. A lever allows heavy load lifted moved small effort. A small effort long distance from the fulcrum can balance large load. Example 3 An electric hoist motor raises load 500kg velocity 2m/s. Determine the rating (power) the motor, assuming the acceleration due gravity 9. From Example 1, Power Mass Acceleration Distance moved Time taken W Power ( ) 85 56 1000 60 7 60 20 000 2 kg m/s m s Power W . 4. Levers and turning force Definition A lever allows heavy load lifted or moved small effort. s s Power W. , The rating the pump motor 20kW.81m/s2 . 9810 The rating the hoist motor 9. Every time open door, turn tap tighten nut with spanner, we exert lever-action turning force. washbasin tap and spanner both provide mechanical advantage through the simple lever action