Kinetic energy. — The energy associated with the motion = -=— in ergs if 

 m is in grams and v in cm/sec. 



Linear acceleration ( a= — J. — The rate of change of velocity. 



Liter. — See Table 32. 



Loschmidt number. — The number of molecules per cm 3 of an ideal gas at 

 0°C and normal pressure = 2.6870 X 10 19 molecules/cm 3 . 



Megabaryes. — Unit of pressure = 1,000,000 baryes = 1 bar = 0.987 at- 

 mosphere. 



Meter. — See Table 31. 



Micro. — A prefix indicating the millionth part. (See Table 901.) 



Micron (/x) = one-millionth of a meter = one-thousandth of a millimeter. 



Mil. — One-thousandth of an inch. 



Mile. — Statute = 5,280 feet ; nautical or geographical = 6,080.20 feet. 



Milli. — A prefix denoting the thousandth part. 



Modulus of elasticity. — Ratio of stress to strain. The dimension of strain, 

 a change of length divided by a length, or change of volume divided by a 

 volume, is unity. 



Mole or mol. — Mass equal numerically to molecular weight of substance. 



Momentum (M = mv). — The quantity of motion in the Newtonian sense; 

 the product of the mass and velocity of the body. 



Moment of inertia (/) of a body about an axis is the Smr 2 , where m is 

 the mass of a particle of the body and r its distance from the axis. 



Newton. — The unit of force in the MKS system = 10 5 dynes. (See Table 

 3, part 2.) 



Pound weight. — A force equal to the earth's attraction for a mass of 1 

 pound. This force, acting on 1 lb mass, will produce an acceleration of 32.17 

 ft/sec 2 . 



Poundal. — The ft-lb sec unit of force. That unbalanced force which acting 

 on a body of 1 lb mass produces an acceleration of 1 ft/sec 2 . 



Pi (tt) =3.1416. (See Table 11.) 



/ dW\ 

 Power. — Activity I p = —j — ) is the time rate of doing work. 



Radian. — An angle subtended by an arc equal to the radius. This angle 

 equals 180%-= 57.29578° = 57° 17'45" =206265'.' 



Resilience. — The work done per unit volume of a body in distorting it to 

 the elastic limit or in producing rupture. 



Slug. — Mass (32.17 lb) acquiring acceleration 1 ft sec" 2 when continuously 

 acted upon by force of 1 lb weight. 



SMITHSONIAN PHYSICAL TABLES 



