44 
I first tried 7^1bs. ; the wire stood the blow due to falls 
of 6' and 6' 6" completely, but broke at the lower clamp 
with 7' 0" and 7' 2". We may take 6' 9" as the breaking 
height. With a 161b. weight dropped o' 6" the wire broke 
at the upper clamp. A 281b. was then tried, falls of 2' and 8' 
respectively, broke it near the upper clamp; 4' 6" broke 
it three feet up the wire in a wounded place ; 5' broke it at 
the top clamp, and 6' was required to break it at the lower 
clamp. This may be taken as a rough confirmation of the 
result that double the velocity is required to break it at 
the lower clamp to that required to cause rupture at the 
upper. Lastly, 411bs. was tried, a fall of 4' 6" broke it at 
the upper clamp, of o' Q" at the lower; take 5' as height 
required to break at the lower. 
In problems of this kind it has been usually assumed by 
some that two blows were equivalent when their vis vivas 
were equal, by others when the momenta were equal; my 
result is that they are equal when the velocities or heights 
of fall are equal. 
Taking the 411bs. dropped o' as a standard, since it will 
be least affected by the clamp, I have taken out the heights 
required for the other weights. Column 1, is the weight in 
lbs. ; 2, the fall observed ; 3, the fall required on vis viva theory; 
4, that required by momentum theory : 
(1) 
(2) 
(3) 
(4) 
41 
5 
5 
5 
28 
5, ,6 .... 
7n 4 
6 
16 
6m0 .... 
12i, 11 
7 1 
1 4. 
28,i 3 . 
linii 
It will be seen that the law here arrived at is the nearest 
of the three, besides which its deviation is accounted for by 
the deadening effect of the clamp. 
But it remains to be explained why the 7|lbs. weight 
could not break the wire at the top at all, whereas the 281bs. 
broke it with a fall of only 2 feet. We should find somo 
means of comparing the searching effect of two blows. For 
this we must look to friction. 
