IS ATTRACTION. 



thrice the time, with nine times the velocity, &c; 

 for, in the first time, there was but one space run 

 over ; the square of 1 is 1 ; at the end of the 

 second time there are four spaces run over, one in 

 the first, and three in the second; the square of 2 

 is 4 : at the end of the third time, there are nine 

 spaces run over; the square of 3 is 9 : and so on. 

 This may be seen in the figure. 



It is found by experiment, that a body falling 

 from a height moves at the rate of 16 T V feet in the 

 first second ; and, as has been shown above, ac- 

 quires a velocity of twice that, or 32^- feet in a 

 second. At the end of the next second, it will 

 have fallen 64f feet, the space being as the square 

 of the time : the square of 2 is 4, and 4 times 16 T ' X 

 is 64f . By the same rule it may be found, that 

 in the third second it will fall 144 feet ; in the 

 next 256 feet, and so on. It is to be understood, 

 however, that by this velocity is meant, what 

 bodies would acquire, if they were to fall through 

 a space where there was no air ; for its resistance 

 considerably diminishes their velocity in falling. 



It has been already shown, that if two forces 

 act uniformly upon a body, they will cause it to 

 move in a straight line ; but if one only, or both, 

 continually change their direction, or intensity of 

 force, the body will describe a curve. If one of 

 the forces uniformly impel the body in a straight 

 line, while the other uniformly draws it towards a 

 centre, the body will move in a circle : an ex- 

 ample of which is seen in a stone in a sling that is 

 swung round by the hand. If at any point of the 

 revolution one of the forces should cease to act, 

 then the body will obey the other force ; if, for 

 instance, the string be let go, the stone will fly off 

 in a straight line, which will be a tangent to the 

 circle in which it moved. 



