Ch6_SekiK

=Physics Classroom Notes=

Lesson 1a(p.1/2): Work
A1: Definition and Mathematics of Work A2: Calculating the amount of work done by a Force
 * What is work, and how can you solve for it?
 * Work is when a force causes an object to be displaced. It is essential that the force be the reason for the displacement, otherwise, it would not be valid. This is because work is made up of three things: force, displacement, and cause.
 * We can solve for work with the equation W = f*d*cos(theta). The f is the force, the d is the displacement, and the cos(theta) the angle between the force and the displacement. It's represented by the unit of Joules.
 * What does displacement have to do with it?
 * Displacement is one of the three main ingredients of work, and is essential when solving for work. It is literally plugged into the equation, and is also taken into account when solving for theta.
 * How does theta factor into work?
 * Theta is needed because it is involved in the equation. It's also plays a big part when looking at forces that have to be broken down into its components. It is important to remember that it is the angle between the displacement and the force itself, or else the answer you get will be wrong when calculating the work.
 * Can it be negative?
 * Yes, it can. However, it happens only when the force hinders displacement, which would be when the angle is around 180.
 * How do you do it?
 * You can calculate it by using the equation W = f*d*cos(theta). If you plug in each variable correctly, you should get the amount of work.

Lesson 2: The Work Energy Relationship
A: Internal vs. External Forces
 * What are Internal Forces?
 * These are those that don't change the total mechanical energy of an object. In this situation, energy is conserved.
 * What are External Forces?
 * Therefore, external forces are those that do change the total mechanical energy of an object.
 * What is the difference between conservative and non conservative forces?
 * Non conservative forces are external forces, because they change the total amount of mechanical energy. Internal forces are conservative because the total mechanical energy doesn't change, just the potential and kinetic.
 * Sample Questions**
 * 1) Correct
 * 2) Correct
 * 3) Correct
 * 4) Incorrect
 * 5) Correct
 * 6) Correct | Incorrect
 * C | C
 * C | C
 * C | C
 * C | C
 * C | Incorrect

Energy Bill Activity
Total kWh used by me daily: 2.55 Daily Cost:$0.2805 Monthly Cost: $8.43 Cost of Electricity: 43 / 390 = 0.110256

Questions Conclusion I'm actually surprised at just how cheap electric is compared to other energy sources. Considering how often we use electricity, it seems almost ridiculous that my electricity consumption is less than ten dollars. However, I understand that it is important to keep things in perspective. Because energy can't be made or destroyed, we have to get electricity from another source of energy, which is what we are soon going to be running out of.
 * 1) The cost of electricity, to me, seems to be not only very low, but also very reasonable for the countless benefits it provides for our lives.
 * 2) My total cost is definitely much higher, as I probably underestimated the time that I use each appliance, as well as probably overlooking many others. Though there isn't one main contributor, there are probably various other electrical machines that I use through the course of my day frequently but shortly, making me overlook them.
 * 3) I think my consumption is very reasonable, though I could definitely spend less time on the computer, as well as turning off the lights when I don't use them.