ENGINEERING DYNAMICS
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Dynamics is "a study of motion," according to Pletta and Frederick , divided into kinematics (a study of motion solely) and kinetics (a study of both motion and the forces that produce it). Dynamics in engineering is universally studied in concert with--usually immediately following--the consideration of statics--the study of forces exerted by and upon bodies at rest. Together, statics and dynamics form engineering (or 'applied') mechanics. Pletta and Frederick introduce dynamics with the seemingly outrageous assertion: "Dynamics is important in all fields of engineering because everything an engineer designs moves in some way during its lifetime." Problems are solved in dynamics with theoretical constructs that differ depending on the types of forces being applied. Those force systems include: constant forces, forces that change with (straight-line or angular) distance, forces that vary with both distance and velocity, ballistics (dealing with the motion of particles reacting solely to gravity), and central force motions (attractions of two bodies for one another). The fundamental consideration in dynamics is the combination of the magnitudes and directions of all forces acting on a body in motion. The representation of physical characteristics having both size and direction is a vector. (Quantities with magnitude only, for which direction of their action is either irrelevant or nonexistent, are scalar quantities.) Speed, m
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a series of forces imparted by nine-iron, six-iron, and three-iron strokes on a golf ball, along with measured accelerations of the ball following each stroke (i) as it leaves the tee or the ground. The mass of the ball would be the Fi's divided by the ai's, and it would be constant. A 16-pound shot struck by a six-iron or a two-iron would not leave the tee nearly so quickly nor would it travel nearly so far; because its mass, its inertia to remain at rest, is so much greater than that of a golf ball. Meriam absolves golf-club manufacturers from such proofs, because the most accurate proofs, he alleges, have been in the "precise account of the motions of the planets".
For many engineering problems, if not the preponderance, the laws of motion can be applied to bodies as if those bodies were actually very small particles with all their mass concentrated at their centers of mass or centroids. "It can be proved that the earth may be considered a particle with its entire mass concentrated at its center. " When more than one particle is involved, and perhaps numerous particles (a truckload of sand grains flying off the side of a bridge springs to mind), a singular resultant, external force acting upon the whole system of partic
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Approximate Word count = 3486
Approximate Pages = 14 (250 words per page)
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