44. 



I first tried TJlbs. ; the wire stood the blow due to falls 

 of 6' and 6' 6" completely, but broke at the lower clamp 

 with 7' 0" and T 2''. We may take 6' 9'' as the breaking 

 height. With a IGlb. weight dropped 5' 6'' the wire broke 

 at the upper clamp. A 281b. was then tried, falls of 2' and 3' 

 respectively, broke it near the upper clamp; 4' 6'' broke 

 it three feet up the wire in a wounded place ; b' broke it at 

 the top clamp, and G' 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' Q" broke it at 

 the upper clamp, of o 6'' 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 4 libs, dropped 5' 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 : 



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 7Jlbs. 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 some 

 means of comparing the searching eff*ect of two blows. For 

 this we must look to friction. 



