52 EXPERIMENTS ON THE LAWS OF MOTION. 



Second Experiment. To find in what manner the 

 velocity is changed if the force changes, take away one 

 of the grammes on the left, and place it upon the right- 

 hand weight. There are now 70 + 1 = 71 gr on the left, 

 and 70 + 4 + 1 = 75^ on the right side. Place tin 

 brass plate four decimetres below the starting point an< 

 the extra weight will again be heard to strike the plai 

 precisely 2 s after starting. In the same time, twice th< 

 space has been passed over ; the velocity is therefoi 

 twice as great as in the last experiment. 



Third Experiment. Remove the remaining gramme 

 weight from the left and place it on the right side. 

 There are now 70 gr on the left, and 70 + 4 -f 1 -f 1 

 = 76 gr on the right ; the moving force is G 81 . The space 

 passed over in 2 s will be found to be 6 decimetres ; that 

 is, the velocity will be three times as great as in the first 

 experiment. 



The moved mass was in these three experiments the 

 same, but the moving forces were in the successive 

 experiments in the proportion of 1 : 2 : 3. The velo- 

 cities produced were in the same proportion. Hence 

 the law : 



TJie velocities produced by forces of different magnitude 

 acting upon the same mass during equal times, are pro- 

 portional to these forces ; or in other words : The 

 velocities produced are directly proportional to the forces. 



In order to observe the effect of the same force upon 

 different masses, we now add weights to each of the 

 70 gr pieces. But here we must consider that not only 

 the weights are set in motion by the moving force, but 

 also the wheel itself; and further, that the motion of the 

 wheel is rotatory, while that of the weights is a motion 



