4 DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



The m.t.s. unit-velocity [Z Z -1 ] is the velocity of i meter per second, or ioo 

 c.g.s. units of velocity. 



The m.t.s. unit of momentum [ML Z _1 ] is the momentum of the mass of a ton 

 moving with the defined unit velocity. It is, therefore, equal to 100,000,000 c.g.s. 

 units of momentum. 



The m.t.s. unit of acceleration [Z Z~ 2 ] is the acceleration of 1 meter per sec- 

 ond, or 100 c.g.s. units of acceleration. The acceleration of gravity is, therefore, 

 in the m.t.s. system, equal to 9.8 approximately, or in rougher approximation 

 equal to 10. 



The m.t.s. unit of force [3/Z Z -2 ] is the force which gives the mass of 

 a ton the defined unit-acceleration. This unit of force is equal 100,000,000 

 c.g.s. units or dynes, i. e., equal to 100 megadynes. Taking 10 for the ac- 

 celeration of gravity, it will represent the weight of a tenth of a ton or of 100 

 kilograms. 



The m.t.s. unit-impulse [J/ZZ -1 ] is the change of momentum given by the 

 defined unit-force during the time of 1 second. This unit-impulse is equal to 

 100,000,000 c.g.s. units of the same quantity. With respect to numerical value 

 and dimensions this unit is identical with that of momentum. 



The m.t.s. unit of force per unit-mass, sometimes called accelerating force 

 [ZZ -2 ], is equal to the defined unit-force per ton of mass which is subject to the 

 action of the force. It is equal, therefore, to 100 c.g.s. units of the same quantity. 

 With respect to numerical value and dimensions the unit of force per unit-mass is 

 identical with that of acceleration. The weight per unit-mass of a resting body is 

 thus numerically equal to the acceleration which the body would take if it was free 

 to fall. On account of this numerical accordance the expression " acceleration of 

 gravity " is used to designate the intensity of gravity measured statically, i. e., the 

 weight per unit-mass of a heavy body. 



The m.t.s. unit-work [J/Z 2 Z~ 2 ] is the work performed by the defined unit- 

 force over the length of 1 meter. This unit- work is 10,000,000,000 c.g.s. units 

 or ergs, i. e., 10,000 meg-ergs. A unit of work in common use is the joule, 

 which is equal to 10 meg-ergs. The m.t.s. unit of work, therefore, is a kilojoule. 

 It represents approximately the work performed by lifting 1 ton 1 decimeter, or 

 100 kilogram-meters. 



The m.t.s. unit of kinetic energy [J/Z 2 Z -2 ] is the kinetic energy of the 

 mass of 1 ton moving with the unit-velocity defined above. The unit-increase of 

 kinetic energy and also the unit-increase of potential energy [J/Z 2 Z -2 ] are 

 obtained as equivalents for a unit of work performed. For this reason we can 

 use numerically the kilojoule as a unit of kinetic and of potential energy as well as 

 of work. When gravity is the acting force, unit-increase of potential energy is 

 obtained by lifting 1 ton the approximate height of 1 decimeter. 



The m.t.s. unit of activity [ML 2 Z -3 ] is the activity of 1 kilojoule per second. 

 This is the kilowatt, an extensively used unit, introduced to replace the old unit 

 of activity, the horsepower. The kilowatt is equal to 10,000,000,000 c.g.s. units 

 of activity, and equal to 1.36 horsepower. 



