282 The Laws of Motion of a Cylinder, &e. 
point, to which it afcended before the firft: But if, 
inftead of this fuppofition, we now imagine it to rife 
after each ftroke to the fame height above the 
column, to which it afcended before, the following - 
is the true method of calculating the time, wherein 
the Block will drive the whole column into the Ob- 
ftacle, putting x == the length of its afcent and 
x 
6 
defcent in free fpace ; time of afcent — ——; time of 
— 
defcent in free fpace = ve; time fpent in pene- 
trating the Obftacle after the firft ftroke == ei 
s 
‘yx Now the fum of thefe three quantities == 
= + eg x «== the time fpent in making 
one ftroke; but, as the time is the fame after every 
ftroke, putting y for the number of ftrokes, we have 
tiyle: Argh “atts Py cr 
; +a+4x iis the whole time; Again, 
the depth penetrated by each ftroke == ¢ x, by what 
has been found above ; andt x y=c, per queft, Hence 
x 
fu c 5 
sary ge Oe are writing thefe values 
x all pee x 
in the expreffion aa tathx oe we have 
c a+ 
yee | 
rar eke ive x ; for the whole time. 
0V_ 
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