F maForce and MotionNEWTON'S LAWS OF MOTIONRev. 0Page 1CP-03NEWTON'S LAWS OF MOTIONThe study of Newton's laws of motion allows us to understand and accuratelydescribe the motion of objects and the forces that act on those objects.EO 1.1STATE Newton's first law of motion.EO 1.2STATE Newton's second law of motion.EO 1.3STATE Newton's third law of motion.EO 1.4STATE Newton's law of universal gravitation.The basis for modern mechanics was developed in the seventeenth century by Sir Isaac Newton.From his studies of objects in motion, he formulated three fundamental laws.Newton's first law of motion states "an object remains at rest (if originally at rest) or movesin a straight line with constant velocity if the net force on it is zero." Newton's second law states "the acceleration of a body is proportional to the net (i.e., sum orresultant) force acting on it and in the direction of that net force." This law establishes therelationship between force, mass, and acceleration and can be written mathematically as shownin Equation 3-1.(3-1)where:F=force (Newton = 1 Kg-m/sec , or lbf)2m=mass (Kg or lbm)a=acceleration (m/sec or ft/sec )2 2This law is used to define force units and is one of the most important laws in physics. Also,Newton's first law is actually a consequence of this second law, since there is no acceleration whenthe force is zero, and the object is either at rest or moving with a constant velocity. Equation 3-1can be used to calculate an objects weight at the surface of the earth. In this special case, F is theforce, or weight, caused by the gravitational acceleration of the earth acting on the mass, m, of theobject. When dealing with this type of problem, we designate the acceleration, g, which equals9.8m/sec or 32.17 ft/sec (g is called gravitational acceleration constant). Thus, equation 3-122becomes F = mg for this case.

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