COMPOUND MOTION. 85 



other, ig actually changed by the motion of the observer ; but the mind, in 

 judging of the real change in place by the difference in the position of tho 

 objects observed, unconsciously confounds tho real and apparent motion. 



5. Why will a tallow candle fired from a gun pierce a board, or target, in the same 

 manner as a leaden bullet will, under the same circumstances? 



When a candle starts from the breach of a gun, its motion is gradually in- 

 creased, until it leaves the muzzle at a high velocity ; and when it reaches the 

 board, or target, every particle of matter composing it is in a state of great 

 Telocity. At the moment of contact, the particles of matter composing tho 

 target are at rest ; and as tho density of tho candle, multiplied by the velocity 

 of its motion, is greater than the density of the target at rest, the greater force 

 overcomes the weaker, and the candle breaks through and pierces a hole in 

 the board. 



6. Why, with an enormouB pressure and slow motion, can you not force a candle 

 through a board f 



Because the candle, on account of its slow motion, does not possess suffi- 

 cient momentum to enable the density of its particles to overcome the greater 

 density of the board ; consequently the candle itself is mashed, instead of 

 piercing the board. 



7. Why will a large ship, moving toward a wharf with a motion hardly perceptible, 

 crush with great force a boat intervening ? 



Because the great mass and weight of the vessel compensates for its want 

 of velocity. 



8. Why can a person safely skate with great rapidity over ice which would not bear 

 his weight standing quietly 7 



Because time is required to produce a fracture of the ice ; as soon as tho 

 weight of the skater begins to act upon any point, the ice, supported by the 

 water, bends slowly under him ; but if the skater's velocity be great, ho 

 passes off from tho spot which was loaded before the bending has reached 

 the point at which the ice would break. 



9. A HBAVT COACH and a light tvagok came in collision on the road. A suit for 

 damages was brought by the proprietor of the wagon. How wasit shown that oxBof tho 

 VEHICLES was moving at an unsafe velocitt ? 



On trial, the persons in the wagon deposed that the shock, occasioned by 

 coming in contact, was so great, that it tfirew them over the head of their horse; 

 and thus lost their case by proving that the faulty velocity was their own. 



10. Why did the fact that they were thbown over tho head of the hobbg by coming 

 In contact with the coach, prove that their velocity was obeateb than it ought to hare 

 been f 



The coach stopped the wagon by contact with it, but the bodies of the per- 

 sons in the wagon, having the same velocity as the wagon, and not fastened to 

 it, contintied to move on. Had the wagon moved slowly, the distance to which 

 they would have been thrown would have been slight To cause them to 

 be thrown a* far as over the head of the horse, would require a great velocity 

 of motion. 



