Ch6_KostmanL

toc = Chapter 6: Work, Energy, and Power =

Lauren Kostman 1/12/12 HW- method 3

__Lesson 1: Basic Terminology and Concepts__
1.) Work: Definition and Mathematics of Work What is the definition of work? - When a force acts upon an object to cause a displacement of the object, it is said that **work** was done upon the objec. - There are 3 key parts to work: force, displacement, and cause. What is the mathematics of work? - F is the force, d is the displacement, and theta is the angle between the force and displacement vector. - Whenever the force and displacement are in the same direction, theta equals zero degrees. - To do work, forces MUST cause displacements. - Negative work is when the force //prevents// displacement. - The unit of work is Joules (J). 1J= 1 N*1m 2.) Work: Calculating the Amount of Work Done by Forces What is the equation of work? - Work can be expressed by the following equation: Work is done when a force acts on an object to cause a displacement. Force, displacement, and the angle between the two are required for work.
 * Summary Lesson 1-a:**

Lauren Kostman January 30, 2012 Classwork- method 3

Lesson 2: Internal vs. External Forces
What's the difference between internal and external forces? - Forces can be categorized as internal or external forces. External forces include the applied force, normal force, tension force, friction force, and air resistance force (contact). Internal forces include the force of gravity and spring force (non-contact). - Forces are categorized into these 2 types due to the change in an object's total mechanical energy when it does work on an object. - When net work is done on an object by an **external** force, the total mechanical energy (KE + PE) of that object cis changed. Positive work- gain energy, negative work, lose energy (potential and/pr kinetic). Due to this, they are nonconservative forces. - When only force doing net work on an object is an **interna**l force, the total mechanical energy remains constant. Energy changes forms- from kinetic to potential or vice versa, but the total of amount of mechanical remains the same. So are conservative forces. EXCERCISES: - __Questions 1-5:__ 1.PE --> KE 2. PE --> KE 3. KE --> PE 4. KE --> PE 5. PE --> KE - __Questions 1-6:__ 1. + work (moves to the right). Change in KE since the ball changes speed. 2. + work (moves in same direction as force). Change in KE and PE. 3. + work (both point to the left). Change in KE. 4. - work (force and displacement are opposite direction). Change in KE. 5. + work (f and d in same direction).Change in KE. 6. + work (f and d in same direction). Change in PE.

Electricity Bill Assignment
2/8/12

__**Data:**__ __**Sample Calculations:**__ Hairdryer: __**Conclusion:**__ Overall, I do not believe that spending a mere $21.25 on electricity per month is excessive; however, there are many major items I excluded from my list, which must be taken into account. For example, I did not include the refrigerator, washing/drying machines, garage door, oven, desktop computer, elliptical, and many more. These appliances use much more power than some items on my list, such as the alarm clock. Had these appliances been accounted for, the expense would have been significantly higher. Additionally, there are five people in my family, and so the cost must by multiplied by five. Nonetheless, in today's society, everything relies on such appliances; although they are costly and can be considered wasteful and harmful for the environment, there's no way to get rid of them completely. Nonetheless, by turning off the lights when leaving a room or using the hairdryer on "low" rather than "high", people can make a big difference in the amount of power used.