WIND VELOCITY AND SURFACE PRESSURE GOLD 



115 



if the particle start from rest. The motion is therefore oscillatory, 

 and the particle moves in a series of cycloidal-like curves, fig. 1. 

 The times to the successive intersections with y = b/a? are 7z/2a, 

 lizjia, etc. For latitude 50 these are about 4 and 12 hours. They 

 are independent of b. If there is damping the motion will be as in 

 fig 2. If the motion is resisted by a force k v proportional to the 

 velocity, the path will be inclined to the .T-axis. Fig. 3 gives the 

 path for the particular case k = a and for a period of time equal to 

 27i/a or 16 hours. 



FIG. I 



FIG. 2 



FIG. 3 



In the case of a constant radial force we have for the motion 



d 2 r /dd\ 2 „ dO 



- — r [ ■ — = K + ar — , 

 dt 2 \dt dt 



d 2 d _ dr dd dr n 



r — + 2 - - + a — = 0, 

 df dt dt pt 



