Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1916-11-11
" 49, ABOUT ANTOMOBH rs "a
EXPERTS EXPLAIN WORKING FORM OF ELECTRICAL.


CBy Special Permission from Motor
Age.1
Power is the rate of doing work,
that is, il is the work done in a given
time divided by the time. When the
rate OF doing work is $4,000 foot
pounds minute the power is equal
TO one horsepower This rate OF
1000 foot pounds a minute is the
same as $50 foot pounds second,
hence, If the rate OF doing work is 800
foot pounds a second the power Is
equal TO, one horsepower.
There are 5000 foot pounds OF work
done in raising 100 pounds OF ma
terial from one floor of a building
TO another floor SO feet above the
first. The work done Is independent
OF the time, but the power reqnired
is dependent upon the time it takes to
do the work. Thus, il 1t takes ~
seconds for the hosting machine to
raise the 100 pounds so feet, the work
done a second will be equal to 5OOOI-
10. -or 500 feet pounds second. Now,
since horse power is $50 foot pounds
n second the horse power in this par
ticular case will be equal to 5OO+5oo,
or 1871 horse power.
The work done in raising the 200
gallons of water q vertical height OF
100 feet was found TO be equal 10
900 900 foot pounds. Now, II TINS
operation is to be performed IN one
hour, the rate OF doing work a minute
will be equal TO the total work done
divided by the time in minutes, or
I 900, 000+60, which Is equal to 16,6666
foot pounds a minute The power the
pump is developing in order to raise
this quantity of water will be equal TO
l6. 666 go, 900, or sos horse power.
This is the power actually required to
lift the water and does not take into
accounA any power lost in the resist
ance OF the pipe due to bends, etc. The
power required to drive the pump VIII
ne greater than the power the pump
develops, as part of the power is lost
within the pump itself; hence, the
horse power OF an electric motor which
may be used In operating this pump
must be quite bit greater than .505
horse power.
Let us suppose that this quantity of
water is to be raised in two minutes
instead of an hour, what horse power
VIII IGQulCQs hCAlCnAbCA1 SlAC VIZ N I
done will be exactly the same but the
power must be greater, as the same
work is TO be done in less time in this
case than in the previous case. The
rate of doing work in this case is equal
to 1000, 0O0+2, or 100000 foot pounds |
a minute. This rate of doing work
divided by $4,000 gives the horse
power, which will be equal to 1915 |
horse power. II is obvious that the |
value Of the horse power required TO
perform a certain operation will in
crease as the time OF doing the work |
increases.
The work done In raising car
weighing 5000 pounds to a vertical
height of so feet we find to be equal
10 250,000 foot pounds. If this opera
ton is to be performed in two minutes |
the rate of doing work will be equal |
TO 250,000a-2, or $4,000 footl
pounds minute. Tho horse power re- |
quired will be equal to 125,000- |
1000, or 3.78 horse power. This is |
the horse power actually required to |
raise the car and does not take into |
account any power required to take
care OF the friction of the elevating |
device. If the car were to be raised In |
80 seconds, or half a minute, the rate |
of doing work would be equal to 1885,
0004HIs, or 100000 foot pounds in
minute. The horse power in this
case, then, is equal TO 250,000-3S,- /
600, orf7. 81 horse power
The work done in drawing the dis /
abled car along the street We find TO
he equal to .O56. 900 foot pounds when /
the pull in the tow rope was 100
pounds and the car was pulled dis,
lance of two miles. Let us suppose
this operation is performed in Is min
utes The rate of doing work will be
equal to 1856. 0004-15. or 10000
foot pounds a minute. The horse pow
er is equal to 7O,400+33,0 1000, or 2.l3
horse power.
Electrical power is the rate of do
ing electrical work-that is, il is the
electrical work done in given time
divided by the time When the rate OF