A lever allows heavy load lifted moved small effort.81m/s2
. 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. this way the crowbar said provide ‘mechani-
cal advantage’.81kW.
9810
The rating the hoist motor 9.81m/s2
. The mechanical advantage of
a simple lever dependent upon the length lever either side the
fulcrum.
,
The rating the pump motor 20kW. A
small effort long distance from the fulcrum can balance large load. 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. Every
time open door, turn tap tighten nut with spanner, we
exert lever-action turning force.
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
.2. lever any rigid body which pivots
or rotates about fixed axis fulcrum.
Levers and turning force
Definition
A lever allows heavy load lifted
or moved small effort.
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
.
Load force Distance from fulcrum
Effort force Distance from fulcrum
This formula can perhaps better understood referring Fig. 4. Applying the principle turning forces lever, obtain the
formula:
Definition
A lever any rigid body which piv-
ots rotates about fixed axis or
fulcrum. washbasin tap and spanner both provide mechanical
advantage through the simple lever action.
Example 3
An electric hoist motor raises load 500kg velocity 2m/s. s
s
Power W. Determine the rating (power) the
motor, assuming the acceleration due gravity 9
