Ch6_GreensteinJ

toc =Honors Physics Chapter 6=

=Physics Classroom Lesson 1=

While we know motion in terms of forces, acceleration, etc., this lesson puts motion in terms of work and energy. Forms of energy include: mechanical, potential, energy, and power. When a force causes displacement, it is called work. Work = force•displacement•cosine(theta)
 * Motion, Work & Energy**

=Notes 1/30= PE s || Energy due to compression or stretching of a spring || 1/2kx 2 ||
 * **Work** || W || Caused when a force is exerted over a distance. Force must have some component along axis of motion. || Fdcosθ ||
 * **Kinetic Energy** || KE || Energy due to motion || 1/2mv 2 ||
 * **Gravitational Potential Energy** || GPE PE g || Energy due to vertical location above or below zero || mgh ||
 * **Elastic Potential Energy** || EPE


 * Measured in Joules


 * **Law of Conservation of Energy**
 * Initial Energy +- Work = Final Energy
 * + Work is work in
 * - Work is work out
 * KE i + GPE i + EPE i +- W = KE f + GPE f + EPE f

=Notes 2/2=


 * F vs. D graph
 * Force versus Distance
 * W = F*d*cosθ
 * Work is the AREA of the graph (Force*Distance=Length*Width)
 * If rectangle, length*width
 * If triangle, 1/2 base*height
 * If trapezoid, 1/2 (base1+base2)*height

=Notes 2/6=
 * Elastic potential energy
 * 1/2 * k * x^2
 * Work goes in
 * Turns into elastic potential
 * Turns into kinetic & gravitational potential
 * Softer spring, smaller k value
 * Harder spring, higher k value
 * Hooke's Law
 * Force of Spring
 * -kx
 * becomes positive, since weight is negative

=** Why Do My Parents Tell Me to Turn off the Lights? **=

Estimate how much electrical energy you consume on a daily basis (ie: what does it cost my parents)
 * __ Objective __**


 * __Data Table__**


 * __ Evaluate __**
 * 1) Does the cost of electricity seem like a lot to you? Discuss this with your friends.
 * 2) No, this cost does not seem like a lot. 33 cents per day is relatively inexpensive, however it is probably high relative to the cost per day if I was very conservative about the energy I use.
 * 3) Keep in mind that this cost only reflects ten appliances. What do you think your total cost actually is? Are there major appliances that you may have excluded from your list of ten that would make a big difference?
 * 4) I think my total cost of energy is closer to $1.27 per day, since I am part of a family of 4. I estimate my share of the electricity is 1/6, since they all use more electricity than me- particularly my dad. Dividing our bill by 6 for my share, and 30 for the days in a month, puts my cost at $1.27. Other major appliances I use are A/C, refrigerator, and the lights in other parts of the house besides my room.
 * 5) If you think your consumption is a lot – what can you change? Do you need/should change?
 * 6) I think that my power consumption is not too high, but could be reduced. If I was more careful of leaving lights on, I suspect I could significantly reduce my cost. For efficiency's sake, I should change my habits.

This activity showed me how much energy different household appliances actually use. It made me realize how much more power is needed compared to what I would have guessed; for example, I would have though that a laptop computer uses more energy than the 2 light bulbs in my room. In reality, the lights use 4X more energy than the laptop! Also, a coffee maker uses 25X more energy than a laptop! I now understand how much energy different tasks require, and how much less power I could use if I took more heed to the power requirements of different appliances. Specifically, turning off lights would account for a huge percentage decrease in my power costs, since I use them so often, yet don't realize how much power they use. Also, I always knew that a microwave uses a tremendous amount of energy, but never would have suspected that it costs more to use a toaster oven. Since the power used is dependent on how long it was used for, a microwave oven actually saves money, since it can heat food in such a short amount of time. Re-heating a piece of pizza takes 30 seconds in a microwave, compared to 5 minutes in a toaster oven. It saves money to use the microwave.
 * __Response__**