178 



OBLIQUE IMPACT. 



100. Oblique Impact. When a stream impinges 

 obliquely on a plane, there are several cases, viz., when the 

 water after impact flows off in one, 

 two, or in more directions. 



(1) Let the plane AB, upon 

 which the stream AC impinges, 

 have a border upon three sides so Fig. 53 



that the water can flow off in one 



direction only. Then the impulse of the water against the 

 surface in the direction of the stream is, from (5) of Art. 99, 



W 



P Z= (1 COS ) (V tf|) 



(1) 



(2) Let the plane AB, upon 

 which the stream DO impinges, 

 have a border upon two sides only, 

 so that the water can flow off in 

 only two directions. The stream 

 will divide itself into two unequal 

 parts, the greater part flowing off 



in the direction CB, and the other in the direction CA. 

 Let W t be the weight of the former, W z the weight of the 

 latter, and W' the whole weight. Then the total impijlse 

 in the direction of the stream, from (5) of Art. 99, is 



Fig. 54 



P = (1 cos) (v 



W 



- + (1 



y 



cos ) (v 



[(i _ cos ) }f j + (1 + cos ) 



W 



- 



(2) 



But the conditions of equilibrium of the two portions of 

 the stream require that the pressures on CB and CA shall 

 be equal to each other ; hence 



or, 



(1 cos ) W l = (1 + cos ) JF 2 , 

 (1 cos ) TFj = (1 + cos ) (W 



