4.2 Conservation of Energy in Isolated Systems
In an isolated system, if the total energy is conserved, does this imply that the kinetic energy is conserved? Recall that kinetic energy is the energy of motion «math xmlns=¨http://www.w3.org/1998/Math/MathML¨»«msub»«mi»E«/mi»«mi»k«/mi»«/msub»«mo»=«/mo»«mfrac»«mn»1«/mn»«mn»2«/mn»«/mfrac»«mi»m«/mi»«msup»«mi»v«/mi»«mn»2«/mn»«/msup»«/math» . Any object that is moving not only has momentum but also has kinetic energy. In previous lessons, you discovered that the total momentum of an isolated system is conserved during a collision. What about kinetic energy-is it also conserved?
Lab Simulation: Kinetic Energy & Collisions
In this lab, the Collision 1D Simulator will be used to collect velocity and mass data from five different collisions. The data will be used to test the conservation of kinetic energy and momentum in each collision.
Problem
Are kinetic energy and momentum always conserved in an isolated system that involves the collision of two objects?
Procedure
Use the Collision 1D Simulator to investigate three different collisions between the same objects and complete the table in LAB 1. The data collected will be used to verify that momentum is conserved and to determine if kinetic energy is also conserved.
On the simulation, toggle "More Data" below the data table.
On the simulation, toggle "Kinetic Energy" from the menu on the right-hand side.
Observations and Analysis
In the chart below, record the initial velocity and final velocity for each object value for the collision. Calculate the initial and final momentum and energy for each object using the mass and velocity values.
Note: Do not worry about what e = elasticity and it is set to 100% in the simulation right-hand menu - it will be discussed in detail in the next section. The value of e will be listed with the other information on the simulation and must be recorded for each collision.
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Collision 1 e =100% |
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Collision 2 e =100% |
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Collision 3 e =100% |
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Conclusion
After completing the simulated lab you should be able to answer the following questions:
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Is momentum conserved in each collision?
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Is kinetic energy conserved in each collision?