334 Mr Vincent, Experiments on Impact. 



The equation, connecting e and u the velocity of approach, is 



e = e — mu, 



where e is the coefficient of restitution for an infinitely small 

 velocity. 



e = -82, 



m = -00018, 



and e is zero when u = 4600 cm. a sec. approx. 

 If v be the velocity of rebound, 



v = e u — tnu-. 



This equation is that of a parabola with its axis vertical, and 

 concave towards axis of u. Its vertex is at the point 



u = -— = 2300 approx. 



e ^ 

 v = -£- = 930 approx., 



while the value of e corresponding to this point would then be 



^ = •41. This shows that if the straight line law for e held 



through a great range then the maximum velocity of rebound 

 would be 930 cm. a sec. 



Fig. 2 exhibits a series of experiments on another lawn tennis 

 ball. The ball with the cloth on does not in this curve give e as 



Vel. of approach in cms. a sec. 



Fig. 2. Lawn Tennis Ball. 



Pts * obtained next day from same ball with cloth on. 

 • after removing cloth. 

 ■ ,, „ and puncturing. 



