A3 MOMENTUM AND ENERGY CONSERVATION

# A3 MOMENTUM AND ENERGY CONSERVATION - EXPERIMENT DYNAMICS...

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EXPERIMENT DYNAMICS: MOMENTUM AND ENERGY CONSERVATION Introduction: “Dynamics” is the study of a body’s motion taking into consideration the effects of its mass, momentum, energy and any external forces acting on it. Newton’s laws give us (directly or indirectly) the concepts of inertia (mass), force (rate of change of momentum), the equivalence of action and reaction, and the concept of conservation of momentum. These, combined with the principle of conservation of energy, represent all the tools necessary for a complete dynamical description of motion. As an example of an interacting system let us consider two gliders with masses m 1 and m 2 on a level air track, moving with velocities u 1 and u 2 , respectively. The total momentum of the system is the vector sum of the individual momenta If the two gliders travel toward each other and collide elastically, they will bounce apart with new velocities and . The total momentum of the system will now be 1 v 2 v 2 2 1 1 i u m u m p + = During an elastic collision, only internal forces act, so that according to the principle of conservation of momentum: . Hence, 2 1 1 v m v m p f + = 2 i p p = f If the two gliders are initially at rest then the left hand side is zero. Further, if the two gliders are initially connected to each other and then forced apart by a sudden force between them (an internal force), such as an explosion or the sudden release of a spring, the gliders will move apart with new velocities v 1 and v 2 . Thus, since p=0 , we must have

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A3 MOMENTUM AND ENERGY CONSERVATION - EXPERIMENT DYNAMICS...

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