48 PROPERTIES AND MAKE-UP OF MATTER 



fluence the direction of its motion, and it will go in the 

 direction of neither force but in a direction between the two. 

 If there are more than two forces, the path of the object 

 acted upon will be the result of the action of all the forces. 

 In the case of the weight and the rubber band we found 

 that the moving weight when not held by the force of 

 the band flew away from the hand. The rubber band con- 

 tinually pulled in toward the hand, while owing to inertia 

 the weight tended to go off in a, straight line. The result 



, , was that the weight 



neither went in toward 

 the hand nor off in a 

 straight line, but in a 

 curved path. 



Planetary Movements. 

 We have seen that 

 the sun is the great 



THREE FORCES IN PLAT 

 See the accompanying diagram. 



FIGURE 19 



center around which the earth and the other members of the 

 solar system revolve. The mass of the sun is so great that 

 the attraction of gravitation between it and the planets holds 

 these with their satellites in their paths and keeps them from 

 flying off into space. In fact the laws of inertia and gravita- 

 tion explain the entire mode of action of the heavenly bodies. 



