Quotation from: General Science

Written by: Bertha M. Clark


The slope of the road is called its grade, and the grade itself is
simply the number of feet the hill rises per mile. A road a mile long
(5280 feet) has a grade of 132 if the crest of the hill is 132 feet
above the level at which the road started.


[Illustration: FIG. 106.--A long, gradual ascent is better than a
shorter, steeper one.]


In such an incline, the ratio of length to height is 5280 / 132, or
40; and hence in order to pull a train of cars to the summit, the
engine would need to exert a continuous pull equal to one fortieth of
the combined weight of the train.

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