Let's set up equations to track and account for what happened:īall 1's velocity: V1 = 30 meters per secondīall 1's Momentum: M1 = 0.145 kg * 30 mps = 4.35 kg m/sīall 2's velocity: V2 = 40 meters per secondīall 2's Momentum: M2 = 0.145 kg * 40 mps = 5.8 kg m/s As we are assuming a perfectly elastic collision, all the kinetic energy of the system remained kinetic and remained within the system. Prior to the collision, each ball had velocity, which is a vector consisting of speed and direction, and each ball had momentum, which is another vector consisting of the product of the ball's mass with its velocity.Īt the instant of impact, a net force acted upon each ball. We will ignore the loss of kinetic energy to noise and deformation of the baseballs. But for our purposes, to keep things simple, let's assume that two baseballs collide head-on and bounce off of each other. In the real world, no collision is perfectly elastic. The second possibility is an inelastic collision. The first possibility is an elastic collision. If two balls collide in mid-air, either of two possibilities may result: (1) All their kinetic energy may remain kinetic and remain within the two-ball system, or (2) some of their kinetic energy may be converted to other forms of energy, such as potential energy, internal energy, heat, sound, etc. (3) Every action will produce an equal and opposite reaction. The more massive the object, the greater will be the amount of net force required to accelerate it. (2) When a net force acts upon an object, the object will accelerate with a change of its speed, of its direction, or of both. Likewise, an object at rest will remain at rest unless a net force acts upon it. (1) An object in motion will remain in motion with the same speed and in the same direction unless a net force acts upon it. These laws (plus the conservation of momentum and of energy) can be used to explain how momentum and velocity are distributed among the objects coming out of a collision: Isaac Newton observed the actions and reactions of objects in motion and recorded his observations as three famous laws. In general, the precise point of contact has a large influence on the collision outcome, and it is in such details that the balls 'decide' which way they're going, and how fast. This is again something you should experiment with, using a pool table or an air table or something similar. When more dimensions are involved, the details of the collision become much more important, even for fully elastic collisions. You will find that the details of the collision affect the outcome, even for the same initial velocities. You can and should experiment with this: take carts on an air rail and make them collide with each other, both elastically (metal-on-metal should be fine, or add springs if not) and inelastically (use blue-tack to make them stick, or add e.g. Even in this simple system the ensuing dynamics are not completely determined, and they depend on how 'elastic' or 'inelastic' the collision is that is, on how much kinetic energy is lost to other energetic channels. The simplest case is in one-dimensional collisions, where both objects are constrained to move along the same line. The way that energy and momentum get split up in the aftermath of a collision depends on the details of the collision itself, and there is nothing in the conservation laws themselves that influences this. The answer is that there is no simple answer.
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