Centre of Gravity 



109 



gravity is lessened. The words "centre of gravity", 

 as used in this statement, require explanation. In the 

 case of a hammer, consisting of an iron head attached 

 to a wooden handle, the centre referred to would not 

 be situated about halfway along the handle, but at a 

 point in the head. This point, through which the total 

 force of attraction exerted by the earth on the hammer 

 and the hammer on the earth may be considered as 

 acting, is called the " Centre of Gravity " of the 

 hammer. 



Fig. 32. 



67. To elucidate further this idea of a centre of 

 gravity some simple experiments may be performed 

 in which its position is determined in the case of certain 

 bodies. 



EXPERIMENT 36. Cut out from millboard of good 

 quality a rectangle, a parallelogram, a circle, and an 

 irregular figure. These figures should not be too small 

 each should have an area of, say, 300 sq. cm. Bore 

 three small holes in the surface of each figure at any 

 points (see Fig. 32). Attach a short length of bent 

 copper wire to a cotton thread to serve as a hook. 



