Some objects, of course, do not stick together, so that less of the internal kinetic energy is removed. This is what happens in automobile accidents. This can also be identified by looking at a collision between two objects, in which one has a spring attached. When the two objects collide, the potential energy in the spring is “released”, resulting in both objects leaving the collision at a higher speed than before. Figure 42 shows this situation:
Figure 42.
In figure 42, the situation is frictionless so that momentum is conserved. The motion is one-dimensional. The potential energy of the compressed spring is released during the collision and is converted to internal kinetic energy. In such cases, the internal kinetic energy is increased for the system.
COLLISIONS IN TWO DIMENSIONS This involves the collision of two objects that do not directly move in a single line. This includes things like the collision of billiard balls, which go off at an angle and often scatter. This is an approach that is not much different from studying kinematics in two dimensions and studying dynamics. The goal is to establish an appropriate coordinate system and to resolve the motion into two different components along an x and y axis. These components are solved separately. In these discussions, no rotation is
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