Unit 5 - Collisions, Impulse, Momentum and its conservation, and the relation of momentum to previous units
Types of Collisions
Elastic - An elastic collision is a collision of two objects in which no kinetic energy is lost. Both momentum and kinetic energy are conserved during an elastic collision.
Inelastic - An inelastic collision is a collision of two objects in which kinetic energy is lost. Only momentum is conserved during an inelastic collision, kinetic energy is not. Perfectly Inelastic - A perfectly inelastic collision is a collision of two objects in which the maximum amount of kinetic energy is lost and the two colliding objects stick together. Only momentum is conserved during an inelastic collision, kinetic energy is not. |
Impulse
Conservation of Momentum
Relating Momentum, Energy, Forces, and Kinematics
The concepts in the momentum unit for this class have been seen in previous units. When a collision occurs, the determining factor of which type of collision it is categorized by is determined by whether or not the kinetic energy of the system has been conserved. If the kinetic energy has been conserved, then the collision is elastic, and if not, then the collision is inelastic. This relates energy to momentum.
The units for momentum are kg * m/s, or N * s. N is the unit for force. This means that a force applied over a certain amount of time is a measure of momentum. Many times in this unit, the impulse will need to be calculated, and in those cases, the force will need to be calculated as well. This can be done using this relationship. When calculating the force acting on a system to try to calculate the impulse, it may also be necessary to calculate the time that a force will be applied to the system. If this is the case, then it may be necessary to use equations from the kinematics unit, such as the Uniformly Accelerated Motion equations from the kinematics unit to find the time. This relates momentum to the unit of kinematics. |
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