Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume IV (1876-1877)
McMurphy, J. G.
Rotation as a factor of motion, pp. -240 PDF (1.5 MB)
238 Wisconsin Academy of &iences, Arts, and Letters. one nor the other, but upon a new axis intermediate between the vertical and horizontal axes, pointed out by the resultant of the parallelogram of angular forces. This is the principle illustrated by the Gyroscope. The ball will describe a curve upon the plane in the same way that a truck rolled upon the ground when the axes cease to be level, begins to curve its path; of course the two cases are quite different, because the curve made by a ball is much less marked than that made by a truck or wheel. There is something of a similar nature seen when a ball is pro- jected from a gun or cast from the hand. Since the middle of the sixteenth century, it has been known that the path of a pro- jectile is a parabola, if no account is taken of the resistance of the air. Templehoff was the first to take into consideration this ele- ment in calculating for projectiles. The resistance of the air in- creases with the square of the velocity until the velocity exceeds 1,300 feet per second, when the resistance is much greater. In experimenting with smooth-bored guns, it was found that rotation had much to do with the motion of the projectile from the muzzle. The only rotation which aided in aiming the gin, and in making calculations reliable, was the axial rotation, which was attained by grooving the-in~terior of the barrel. In the practice of gunnery with a smooth-bored gun there was allowed enough space around the ball for free and easy motion. It was called windage. This windage allowed the ball to ballot slightly from side to side as it passed through the barrel. At each point of balloting the ball received a rotary motion by being retarded on that side next the tangent barrel. The last touch imparted the final rotation, or that which -continued through the space traversed by the ball. If the last ballot was upon the right side of the barrel the ball received a right hand rotation. It also received an impulse toward the left of the mark aimed at by the touch on the right side. But while the left side of the ball is moving forward at a much greater velocitv than the center on ac- count of the right hand rotation, the right side is moving much slower than the center on account of the same rotation. The left side, therefore, encounters a greater resistance than the right side. The air in front and to the left is compressed, and accumulated
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