Energy and Momentum
These are two topics which form a cornerstone of physics. They represent an introduction to one of the most basic assumptions in physics: The conservation laws. All of the myriad rules governing how things interact and move are based on these principals. These laws go beyond application to mechanics, however, they also connect the various other topics together.
Energy, for example, is conserved (neither created nor destroyed). Energy lost from an electric field can be used to increase mechanical energy. Energy gained in the form of heat may from a loss in mechanical or magnetic energy. In "modern physics" energy and mass are shown to be equivalent so that a loss of mass in a nucleon can contribute to kinetic energy and so on.
| Energy | |
| Introduction A Glenbrook review of the basic concepts of Work-Energy connection | A bit more detail. This is a university site which is more mathematical |
| Why is the coordinate system (choice of the zero point) important? Review of this concept. | What happens when it doesn't "add up?" have you considered the non-conservative forces and the non-conservative work done? |
| Here is a simulation of a frictionless roller coaster. | |
Another abstract concept of conservation is the notion of momentum. It, too, is conserved when objects interact such as through a collision. The difference here is that, unlike energy, momentum is a vector quantitiy so information about the state of motion is retained.
| Momentum | |
| Simulations illustrating the conservation of momentum in various situations. This site is heavily JAVA powered. | 2D Collisions is just the logical extension of 1D momentum. Now the vectors must add up not just the scalar values. |
| Relativity. We will revisit this topic from time to time but this is the start of how we really calculate momentum. | |
What happens in linear dimensions happens with rotation as well. Angular momentum is the special case of something that spins must retain its state of spin unless acted upon by a twisting force (torque).
| Angular Momentum | |
| Momment of Inertia is just the rotational analog of mass. Apply a twisting force and an object will resist turning proportional to its inertia. | Moment of Inertia for some common objects. Click on the object and be sent to a calculator to figure the M.I. of that object. |
| Does an object which has only linear momentum have angular momentum? What is Kepler's second law anyway? | |
| Relativity. We will revisit this topic from time to time but this is the start of how we really calculate momentum. | |
Momentum
Magnetism