118 SUDDEN COMPRESSION OF A MASS OF AIR. 



2. A mass M of a substance of specific heat S and tem- 

 perature T, is immersed in a vessel of water, m' and m 

 being the masses of the vessel and of the water in it, and 

 t' their common temperature and s' the specific heat of the 

 vessel. Find the temperature t of the whole after immer- 

 sion. _ MST + mi' + m's't' 



A?IS t -*-n ! I j T~~~ ' 



MS + m + m s 



3. A glass vessel weighing 1 Ib. contains 5 oz. of water, 

 both at 20, and 2 oz. of iron at 100 is immersed. What 

 is the temperature of the whole, taking .2 as the specific 

 heat of glass and .12 of iron ? Ans. 22^. 



The following are approximate values of the specific heats 

 of a few substances : 



Water, . . ...... 1 



Thermometer-glass, .... 0.198 



Iron, ......... 0.114 



Zinc, ......... 0.1 



Mercury, ....... 0.03 



Silver, ......... 0.06 



Brass, ........ 0.09 



(Besant's Hydrostatics, p. 147.) 



69. Sudden Compression of a Mass of Air. A. 



mass of air being suddenly * compressed or dilated, it 

 is retired to find the new pressure and temperature. 



Let p, p, T be the pressure, density, and absolute tem- 

 perature at any stage of the process ; p', p', T' the new 

 pressure, density, and temperature ; and. let dTbe the change 

 of temperature due to the change dp in p. Then we have 



* If the compression takes place in a non-conducting vessel, so that no heat 

 lost or gained, the compression need not be rapid. 



