Ch6_LefflerM

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 Chapter 6!!!

Part A:
** Definition and Mathematics of Work ** WORK: When a force acts upon an object to cause a displacement of the object, it is said that **work** was done upon the object. In order for a force to qualify as having done //work// on an object, there must be a displacement and the force must //cause// the displacement. ex. - a horse pulling a plow through the field Work Equation: w=F*d*[cos(theta)]
 * 1) force
 * 2) displacement
 * 3) cause

 **The Meaning of Negative Work**The //negative// of negative work refers to the numerical value that results when values of F, d and theta are substituted into the work equation. Theta is 180 degrees for negative work. **The Joule is the unit of work.****1 Joule = 1 Newton * 1 meter****1 J = 1 N * m**

<span style="font-family: 'Comic Sans MS',cursive;"> <span style="font-family: 'Comic Sans MS',cursive;">Part B: three quantities must be known in order to calculate the work.
 * Calculating the Amount of Work Done by Forces **
 * <span style="font-family: 'Comic Sans MS',cursive;">force
 * <span style="font-family: 'Comic Sans MS',cursive;">displacement
 * <span style="font-family: 'Comic Sans MS',cursive;">the angle between the force and the displacement (theta)
 * <span style="font-family: 'Comic Sans MS',cursive;">Actual Equation :
 * <span style="font-family: 'Comic Sans MS',cursive;">Work= force•displacement•cosine(theta)

<span style="font-family: 'Comic Sans MS',cursive;"> Lesson 2a: Method 1

<span style="color: #0099cc; font-family: 'Comic Sans MS',cursive; font-size: 14px;">Internal vs. External Forces
<span style="font-family: 'Comic Sans MS',cursive;">All the types of forces could be categorized as: <span style="font-family: 'Comic Sans MS',cursive;"> <span style="font-family: 'Comic Sans MS',cursive;">Forces can be categorized as internal forces or external forces. All **external forces** include the applied force, normal force, tension force, friction force, and air resistance force. And for our purposes, the **internal forces** include the gravity forces, magnetic force, electrical force, and spring force. While this is a simplistic approach, it is an approach that will serve us well in our introduction to physics. <span style="font-family: 'Comic Sans MS',cursive;">If the work is //positive work//, then the object will gain energy. If the work is //negative work//, then the object will lose energy. The gain or loss in energy can be in the form of __ [|potential energy] __, __ [|kinetic energy] __, or both. Under such circumstances, the work that is done will be __equal__ to the change in mechanical energy of the object. External forces are sometimes referred to as **nonconservative forces**. <span style="font-family: 'Comic Sans MS',cursive;">When the only type of force doing net work upon an object is an internal force (for example, gravitational and spring forces), the __ [|total mechanical energy (KE + PE)] __ of that object remains constant. When the only forces doing work are internal forces, energy changes forms - from kinetic to potential (or vice versa); yet the total amount of mechanical is conserved. Because internal forces are capable of changing the form of energy without changing the total amount of mechanical energy, they are sometimes referred to as **conservative forces**. <span style="font-family: 'Comic Sans MS',cursive;">In the following descriptions, the only forces doing work upon the objects are internal forces - gravitational and spring forces. Thus, energy is transformed from KE to PE (or vice versa) while the total amount of mechanical energy is conserved. Read each description and indicate whether energy is transformed from KE to PE or from PE to KE. Click the mouse to check your answers. <span style="font-family: 'Comic Sans MS',cursive;">Why Do My Parents Tell Me To Turn Off The Lights?
 * <span style="font-family: 'Comic Sans MS',cursive;">contact forces
 * <span style="font-family: 'Comic Sans MS',cursive;">action-at-a-distance forces.
 * action-at-a-distance force is when objects are not physically touching.
 * < <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Internal Forces** ||< <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**External Forces** ||
 * < <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Fgrav****Fspring** ||< <span style="color: #ff0000; font-family: 'Comic Sans MS',cursive;">**Fapp****Ffrict****Fair****Ftens****Fnorm** ||
 * __ Objective __**
 * Estimate how much electrical energy you consume on a daily basis (ie: what does it cost my parents)
 * No More than 5 dollars.
 * __ What to do? __**
 * Identify 10 electrical appliances you use on a daily basis and identify their power rating (in Watts).
 * I only found seven that were specifically me.
 * Hair Straightener - 35 W
 * T.V. - 120 W
 * Lights - 60 W
 * Charger for Laptop - 60 W
 * iPod Speakers - 30 W
 * Router - 22 W
 * Microwave - 150 W


 * What does this cost your parents?
 * This costs my Dad about $18
 * Look at your household electric bill. Find two numbers:
 * the total dollar amount due
 * $61
 * kWh consumed that month.


 * 1) Costs of Electricity.
 * 2) Calculate the average cost per kWh by dividing the dollar amount by the kWh consumed. This is approximately what each kWh costs your family. (Note: this figure includes fees and taxes, too). The cost will probably be between $0.10-$0.20 per kWh – depending on how much electricity you use. Electricity costs more if you exceed a certain usage.
 * 3) Each kWh cost my Dad about 0.12 cents
 * 4) Compare the two values. Why are they different?


 * 1) Multiply the kWh you use per day by the cost per kWh to determine what you cost your parents.


 * __ Evaluate __**
 * 1) Does the cost of electricity seem like a lot to you? Discuss this with your friends.


 * 1) 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?


 * 1) If you think your consumption is a lot – what can you change? Do you need/should change?


 * __ Homework __**
 * 1) Talk to your parents about this.


 * 1) Post your data table and calculations, typed up on your Ch 6 wiki (use equation editor).


 * 1) Write something too – tell me your thoughts – a short paragraph. Typed.