Ch6_RubensteinD

Chapter Six toc =__Homework 1/12/12 Work, Energy, and Power Lesson 1a__=

- The effect that work has upon energy of any object is what is being investigated in the resulting velocity and/or height of the object can then be predicted from energy information - Work- when a force acts upon an object to cause a displacement of the object - Key factors to work are: force, displacement, and cause - In order for a force to qualify as having done work on an object there must be a displacement and the force must have caused the displacement - Mathematically work is defined by w = f*d*cos(theta) - To do work, forces must cause the displacement - The equation for work lists three variables - each variable is associated with one of the three key words mentioned in the definition of work - On occasion, a force acts upon a moving object to hinder a displacement This is caused negative work - The nagative of negative work refers to the numerical value that results when the equation is used - The JOULE is the unit of work - 1 joule = 1 Newton * 1 meter - This can be done using the same equation that was taught in the first part of this lesson, but it has to be used differently to be applied to different situations - When there are numerous forces, a free-body diagram is used - Next to the FBD, it must be stated whether or not the force is doing work on the object and if so the amount of work it is doing
 * What is work and how does mathematics apply to the situation?**
 * How do you calculate the amount of work done by different forces?**

In this lesson, the concepts of work and energy were introduced. Work is what happens when a force causes an object or a system to be displaced. Additionally, the equation w = f*d*cos(theta) can be used to find the numerical value of work in different situations. Joules are used as the units for work, and 1 joule is equal to 1 Newton * 1 meter. Finally, FBDs are used for work as well as they help keep organized what forces are doing work on the object.

=__Classwork/Homework 1/30/12__=


 * __Top of Worksheet:__**


 * __Physics Classroom (Internal vs. External Forces):__**

- External forces include the applied force, normal force, tension force, friction force, and air resistace force - The internal forces include the gravity forces, magnetic force, electrical force, and spring force - External: Fapp, Ffrict, Fair, Ftens, Fnorm - Internal Force: Fgrav, Fspring - We categorize them based on whether or not their presence is capable or changing an object's total mechanical energy - We can categorize into internal forces and external forces - The importance of categorizing a force as being either internal or external is related to the ability of that type of force to change an object's total mechanical energy when it does work upon an object - When net work is done upon an object by an external force, the total mechanical energy of that object is changed - If the work is positive work, then the object will gain energy - If the work is negative work, then the object will lose energy - When the only type of force doing net work upon an object is an internal force, the total mechanical energy of that object remains constant - In such cases, the object's energy changes form - This is referred to as energy conservation - When the only forces doing work are internal forces, energy changes forms from kinetic to potential or vice versa
 * Whats the difference between internal and external forces?**
 * How do you categorize these forces?**

In this lesson I learned about the difference between external and internal forces and how they can each be categorized. External forces include forces such as normal, tension, friction, and air resistant forces. Internal forces include forces such as gravitational and spring forces. With external forces, the object's total mechanical energy will change. With internal forces, the total mechanical energy will remain constant, however, the object's energy will change forms.

1. PE to KE (correct) 2. PE to KE (correct) 3. KE to PE (correct) 4. KE to PE (correct) 5. PE to KE (correct) 6. Positive work (correct) PE (wrong) 7. Positive work (correct) Both (correct) 8. Positive work (correct) KE (correct) 9. Negative work (correct) KE (correct) 10. Positive work (correct) PE (wrong) 11. Positive work (correct) Both (wrong)
 * Exercise Results:**

=Energy Bill Activity=

60 Watt light bulb 3500 Watt blowdryer 100 Watt can opener 1500 Watt toaster 4 Watt clock 100 Watt IPod charger 25 Watt flat iron 350 Watt fridge 200 Watt TV 240 Watt computer charger
 * Identify 10 electrical appliances you use on a daily basis and identify their power rating in Watts.**


 * Data and Calculations:**


 * Total Dollar Amount Due for November 2008:** $115.69
 * kWh Consumed That Month**: 1020


 * Calculate the average cost per kWh:** $.056 per kWh
 * Value on Electric Bill**: $.113 per kWh

These values are different because on the electric bill it shows how much 600 kWh would cost and not just one. Also, my calculations did not consider the fact that fees and taxes are included as well.

I cost my parents $1.29 a day.

Yes, although at first glance $1.29 does not seem like a lot of money, that only covers one day's worth of electricity. However, this amount adds up very fast and will eventually become very expensive.
 * Evaluate:**

The total cost is probably a lot more than this. I only accounted for 10 appliances in my calculations, however, in reality my family uses much more than ten appliances per day. I definitely excluded some major items such as computers and telephones, since those are used very often in my house. I think that this amount of consumption should definitely be reduced. To do this, people in my family can cut down their use of certain devices, as well as doing simple things such as remembering to turn off the lights.

My parents were just as surprised as me by the amount of energy we consume every day. They agreed that it is definitely necessary to cut down the amount of energy we use by remembering to do basic things such as always turning off lights and not watching TV/using the computer as much. Personally, I feel that this activity definitely opened my eyes to the amount of energy that is consumed in an average household per day. Although people never realize how much energy they are actually using, in reality they actually are using a great amount that most definitely should be reduced. Before this activity, I never considered how much kWh was being consumed by using basic appliances such as a phone charger and a refrigerator. However, I now realize how much energy is actually being consumed while I use these electronic appliances and I will definitely be more aware of how much time I spend on them.
 * Homework:**