EXPERIMENTS ON THE MOTION OF FALLING BODIES. 63 



the force which causes the acceleration ceases to act. 

 The weights move now solely in virtue of their iner- 

 tia, the velocity ceases to increase, and the spaces now 

 traversed show what velocity has been acquired. When 

 the plate is opposite to 0*5, and the extra weight thus 

 ceases to act at the end of the first second, the descending 

 weight will arrive at the end of the next second at 1*5, 

 at the following at 2'5 7 and so on; a velocity of l docim is 

 hence acquired during the first second. When the 

 plate is opposite to 2*0, and the extra weight is thus 

 removed after 2 seconds 7 the descending weight will 

 arrive at 4, G, 8, etc. at the end of the third, fourth, 

 fifth, etc. second. When the plate is opposite to 4*5, 

 the descending weight will arrive at the end of the 

 next three seconds respectively opposite to 7*5 7 10' 5, 

 13 -5; when the extra weight is stopped at 8*0 on the 

 scale, the descending weight will move in the next 

 second to 12'0, and so on. 



The results calculated in the above table may be 

 tested in this manner by observation. Care must be 

 taken that the thread passes exactly through the middle 

 of the holes in the extra weights, otherwise friction will 

 be produced; if possible a single extra weight of 6 gr should 

 be used, but this is not absolutely necessary. The ve- 

 locity after the first second is rather small, and a small 

 inaccuracy in fixing the plate for the reception of the 

 extra weight may cause perceptible differences in the 

 velocity of the descending weight from the expected 

 result; the experiments are from this cause more suc- 

 cessful for the velocities obtained after two, three, etc. 

 seconds. 



The circumstances which accompany the free fall of 





