116 Domestic Science 



in Experiment 36, push a pin through each of the points 

 of intersection of the lines drawn on each figure. By 

 moving the pin gently about, make each of the holes 

 just large enough for the figures to move freely around 

 the pin. Pin each figure in turn to the vertical board 

 previously used. Note the position first taken up by 

 each figure. Turn each into a fresh position by making 

 it revolve around the pin. Note what happens. If the 

 centre of gravity has been determined with sufficient 

 care, and the hole has been made exactly at the right 

 place, it will be found that the figure remains steady 

 in the new position. That is to say, bodies supported 

 at their centres of gravity are in neutral equilibrium. 



Make another hole with the pin in each figure, not 

 at the centre of gravity, and pin each in turn to the 

 board as before. Note the position taken up. Cause 

 each figure to revolve around the pin for a short distance, 

 and then release it. Each will be seen to swing back- 

 wards and forwards after release and will finally come 

 to rest in the same position as that first taken up. 

 Note where the centre of gravity is situated with regard 

 to the pinhole in each case when the figure comes to 

 rest. In every case the centre of gravity will be seen 

 to be vertically beneath the hole. From this observa- 

 tion we learn that bodies supported at one point, not 

 situated at their centres of gravity, are in a position 

 of stable equilibrium when the centre of gravity is 

 immediately under the point of support. 



Leaving the figures pinned to the board as just 

 described, carefully adjust the position of each in turn 

 so that the centre of gravity is vertically over the point 

 of support. When very carefully done, it may be 

 shown that the figure will remain in this position as 

 long as no disturbing influence comes into action. The 



