Mr Vincent, Experiments on Impact. 



341 



and consequently varies as I. The time taken in making a dent is 

 therefore independent of the velocity of impact. The time is 



irl ttcI- 

 ¥a or \Wu ' 



which equals ofjr- 



For curve A Fig. 6 the time is 1*85 x 10~ 4 sees, and for curve D 

 it is 14 x 10 -4 sees. 



The law of proportionality between u and d' 2 may be used to 

 determine e. By giving the surface of the lead block a slight tilt 

 from the horizontal we can ensure that successive dents do not 

 occur too near each other, and if this inclination is slight the 

 impact is still practically direct. The velocity of impact at the 

 (n + l)th dent is the velocity of recoil from the nth dent; and 

 knowing the value of b we can compute several values of e from 

 the measurements of successive dents. The calculations and 

 observations are tabulated below for the lead used in curve B, 

 Fig. 6. 



The values of e given in column V. are set out in Fig. 7 

 against the values of the velocity in column I. as the abscissae. 

 Alternative ordinates from column VI. are distinguished by 

 crosses in the three cases in which any difference in the value 

 of e occurs. The alternative values for the cases of velocities 



From 2nd <$■ 

 3rd dents From 1st and 2nd dents 



* — 

 ^-- 



O-^-^.^^ 



B-— S 



Vel. of Approach in cms. a sec. 

 Fig. 7. 



326, 678 and 950 have now to be combined with the other values 

 to draw a curve. This is more regular if drawn through the 

 crosses in these cases, and these points indicate probably the 

 better value for e in each case. 



The velocity of impact in the case of second dent can be 

 computed in two ways which are given in columns VIII. and IX., 

 and thus to the ordinates in column XI. we have two alternative 

 sets of abscissas, those in columns VIII. and IX. 



VOL. x. PT. vi. 25 



