Kinetic Energy

For some reason by pictures are up there ^^^^ but their relevance will be explained later. We started off class by reviewing the questions we started yesterday on power. These questions also reviewed calculating work quite nicely as we discovered that work needs to be calculated in order to solve for power.

Next, we expanded on what we had previously learned about energy. We we introduced to some new concepts:

1. Kinetic energy- the energy of motion. Ex: a ball rolling. Formula: $Ek=1/2mv^2$ Kinetic energy is a scalar quantity :)
2. Potential energy- the energy of rest. Ex: a ball being held in the air.
3. Change in energy= (final kinetic energy- initial kinetic energy) or $1/2(mvf^2-mvi^2)$

We learned that work= change in energy. This concept is important because it can make problem solving a lot easier. For example, we were given a problem that gave us the variables mass, initial velocity, and final velocity and were asked to solve for work. Instead of calculating force, displacement, and acceleration to eventually find work, we were able to simply calculate change in energy using $1/2(mvf^2-mvi^2).

Finally, we reviewed and expanded on our knowledge of collisions. We learned how energy fit into each type and were introduced to one new type:

• elastic collision- the two bodies don't stick together after the collision. There is no change in kinetic energy. Ex: the bat hitting the ball
• inelastic collision- the two bodies stick together after collision, some energy is lost. The energy lost is usually in the form of sound, heat, or light. Ex: the cars stuck together
• completely inelastic collision- the two bodies stick together after the collision but no energy is lost. Ex: the spaceship stuck in the planet.

Paige is next, I think.