38 AXSWEKS TO PRACTICAL QUESTIONS 



The flow of water through the narrower part of the siphon 

 would be faster than through the wider part. 



21. What would be the effect of malting a small hole in 

 the top of a diving-bell while in use ? 



It would allow the compressed air to be pushed out by the 

 pressure of the water below. 



22. The pressure of the atmosphere being 1.O3 kg. per 

 sq. cm. 9 what is the amount on 1O sq. meters ? 



103,000 kg. 



ACOUSTICS. 



184 1. Why can not the rear of a long column of 

 soldiers keep time to the music ? 



Because it takes time for the sound-wave to pass down the 

 column, and hence those in the rear do not hear the music as 

 soon as those in front. 



2. Three minutes elapse between the flash and the re- 

 port of a thunderbolt : hoiv far distant is it ? 



If the air is at the freezing point, the distance is 

 1,090 ft, x 60 x 3 = 196,200 ft. 



5. Five seconds expire between the flash and report of 

 a gun: what is the distance? 



1,090 ft. x 5 = 5,450 ft. 



4. Suppose a speaking-tube should connect tivo villages 

 1O miles apart. How long would it take a sound to pass 

 that distance ? 



52,800 ft +- 1,090 ft. = 48.4 (sec.) 



This is of course a theoretical case. The initial energy 

 manifested as sound would be transformed into other modes of 

 energy, such as heat, before complete transmission through so 

 great a distance in a speaking-tube, unless the sound be more 

 intense than that of the human voice usually is. 



