| GENE SLOVERS US NAVY PAGES CORIOLIS FORCE |
| CORIOLIS FORCE In classical mechanics, an inertial force described by the 19th-century French engineer-mathematician Gustave-Gaspard Coriolis in 1835. Coriolis showed that, if the ordinary Newtonian laws of motion of bodies are to be used in a rotating frame of reference, an inertial force acting to the right of the direction of body motion for counterclockwise rotation of the reference frame or to the left for clockwise rotation--must be included in the equations of motion. The effect of the coriolis force is an apparent deflection of the path of an object that moves within a rotating coordinate system. The object does not actually deviate from its path, but it appears to do so because of the motion of the coordinate system. The Coriolis effect is most apparent in the path of an object moving longitudinally. On the Earth an object that moves along a north-south path, or longitudinal line, will undergo apparent deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. There are two reasons for this phenomenon: first, the Earth rotates eastward; and second, the tangential velocity of a point on the Earth is a function of latitude (the velocity is essentially zero at the poles and it attains a maximum value at the Equator). Thus, if a cannon were fired northward from a point on the Equator, the projectile would land to the east of its due north path. This variation would occur because the projectile was moving eastward faster at the Equator than was its target farther north. Similarly, if the weapon were fired toward the Equator from the North Pole, the projectile would again land to the right of its true path. In this case, the target area would have moved eastward before the shell reached it because of its greater eastward velocity. An exactly similar displacement occurs if the projectile is fired in any direction. The Coriolis deflection is therefore related to the motion of the object, the motion of the Earth, and the latitude. The Coriolis effect has great significance in astrophysics and stellar dynamics, in which it is a controlling factor in the directions of rotation of sunspots, It is also significant in the earth sciences, especially meteorology, physical geology, and oceanography, in that the Earth is a rotating frame of reference, and motions over the surface of the Earth are subject to acceleration from the force indicated. Thus, the Coriolis force figures prominently in studies of the dynamics of the atmosphere, in which it affects prevailing winds and the rotation of storms, and in the hydrosphere, in which it affects the rotation of the oceanic currents. It is also an important consideration in ballistics, particularly in the launching and orbiting of space vehicles. In modern physics, application of a quantity analogous to Coriolis force appears in electrodynamics wherever instantaneous voltages generated in rotating electrical machinery must be calculated relative to the moving reference frame: this compensation is called the Christoffel voltage. DICTIONARY DEFINATION Main Entry: Coriolis force Function: noun Etymology: Gaspard G. Coriolis died 1843 French civil engineer Date: 1923: an apparent force that as a result of the earth's rotation deflects moving objects (as projectiles or air currents) to the right in the northern hemisphere and to the left in the southern hemisphere Main Entry: Co•ri•o•lis effect Pronunciation: "kOr-E-'O-l&s-, "kor- Function: noun Date: circa 1946: the apparent deflection of a moving object that is the result of the Coriolis force THE FOLLOWING BY GENE SLOVER Coriolis force was predicted by Gaspard G. Coriolis who died in 1843. He was a French civil engineer. His prediction was about 1835. It is an apparent force that as a result of the earth's rotation deflects moving objects (as projectiles or air currents) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. The body in question does not have to rotate to be affected by this force. Coriolis effect is the result of Coriolis force and Coriolis effect is what you correct for not Coriolis force. So Coriolis effect is the apparent deflection of a moving object that is the result of the Coriolis force. The theory was proven about 1922 or 1923. As far as I know there were no corrections made to the fire control problem until the mid 30’s and then only to 8” guns and above is it considered important. In fire control range only is affected if the firing is east or west. Bearing only if the firing is north or south. At 45 degrees from north or south then bearing and range are affected. Has to do with planes of rotation of different diameters rotating about the same center point. NO 1 If you have a ball, called earth, that is of such diameter that it is about 24,000 miles around it at its equator, and it rotates 1 time every 24 hours and the rotation is to the east, then you can say that the eastward horizontal velocity at its equator is about 1,000 miles per hour. An object on the earths surface at the equator, has the same eastward horizontal velocity as the surface of the earth that it is sitting on. When this object is launched, such as a projectile from a gun, this eastward horizontal velocity is superimposed on the projectile and into its flight. Since at the equator the eastward horizontal velocity is about 1,000 miles per hour, the projectile when airborne retains this eastward horizontal velocity of 1,000 miles per hour throughout its flight. Firing north from the equator. At the equator the eastward horizontal velocity is about 1,000 miles per hour. At some point directly north of the equator, towards the north pole, where the circumference of the earth would be 1/2 of the circumference at the equator, or 12,000 miles, the eastward velocity of the surface of the earth is about 500 miles per hour because the diameter of the earth is smaller at that point. A gun fired due north from the equator, has imparted an eastward horizontal velocity of 1,000 mph to the projectile. A time of flight for this projectile of 1 hour means that the projectile will travel eastward 1,000 miles due to the imparted eastward horizontal velocity of 1,000 mph to the projectile at launch. The point that the gun was fired at however has an eastward velocity of only about 500 miles per hour because the diameter of the earth is smaller at that point. So in the 1 hour time of flight the point being fired at moves 500 miles to the east. The projectile however has moved east by 1,000 miles due to the imparted eastward horizontal velocity at launch of about 1,000 miles per hour. So the projectile lands 500 miles east of the point being fired at due to the difference in speeds of the projectile and the point on earth being fired at. The projectile lands 500 miles to the right of the point being fired at. The projectile is then said to have RH drift due to the effect of Coriolis Force. NO 2 Firing south from the equator. At the equator the eastward horizontal velocity is about 1,000 miles per hour. At some point directly south of the equator, towards the south pole, where the circumference of the earth would be 1/2 of the circumference at the equator, or 12,000 miles, the eastward velocity of the surface of the earth is about 500 miles per hour because the diameter of the earth is smaller at that point. A gun fired due south from the equator, has imparted an eastward horizontal velocity of 1,000 mph to the projectile. A time of flight for this projectile of 1 hour means that the projectile will travel eastward 1,000 miles due to the imparted eastward horizontal velocity of 1,000 mph to the projectile at launch. The point that the gun was fired at however has an eastward velocity of only about 500 miles per hour because the diameter of the earth is smaller at that point. So in the 1 hour time of flight the point being fired at moves 500 miles to the east. The projectile however has moved east by 1,000 miles due to the imparted eastward horizontal velocity at launch of about 1,000 miles per hour. So the projectile lands 500 miles east of the point being fired at due to the difference in speeds of the projectile and the point on earth being fired at. The projectile lands 500 miles to the left of the point being fired at. The projectile is then said to have LH drift due to the effect of Coriolis Force. |
| EXTRACTS OF RANGE TABLES FOR 8"/55 GUN ABOUT HALF WAY DOWN THE TABLE YOU WILL FIND CORRECTIONS IN YARDS OF RANGE AND DEFLECTION DUE TO THE EARTHS ROTATION IN BOTH THE NORTH AND SOUTH LATITUDES. |