Ch6_LeibowitzG

= **__Lesson 1-__** **//Work, Energy, and Power//** = **(Method 1a)** >>
 * **Work**
 * **Definition and Mathematics of Work**
 * **Calculating the Amount of Work Done by Forcestoc**

**What is work and how does mathematics apply to the situation?** - 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 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- The JOULE is the unit of work <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- 1 joule = 1 Newton * 1 meter <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;"> <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**How do you calculate the amount of work done by different forces?** <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- 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 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- When there are numerous forces, a free-body diagram is used <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- 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

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">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.

= <span style="font-family: 'Times New Roman',Times,serif; font-size: 22px;">**__Classwork-__** **//1/30/12//** =

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**__Top of Worksheet:__**

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**__Physics Classroom (Internal vs. External Forces):__**

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**Whats the difference between internal and external forces?** <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- External forces include the applied force, normal force, tension force, friction force, and air resistace force <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- The internal forces include the gravity forces, magnetic force, electrical force, and spring force <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- External: Fapp, Ffrict, Fair, Ftens, Fnorm <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- Internal Force: Fgrav, Fspring <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;"> <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">**How do you categorize these forces?** <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- We categorize them based on whether or not their presence is capable or changing an object's total mechanical energy <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- We can categorize into internal forces and external forces <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- 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 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- When net work is done upon an object by an external force, the total mechanical energy of that object is changed <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- If the work is positive work, then the object will gain energy <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- If the work is negative work, then the object will lose energy <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- 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 <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- In such cases, the object's energy changes form <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- This is referred to as energy conservation <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">- When the only forces doing work are internal forces, energy changes forms from kinetic to potential or vice versa

<span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">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.

<span style="font-family: 'Times New Roman',Times,serif;">__ **Exercise:** __ <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">1. PE to KE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">2. PE to KE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">3. KE to PE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">4. KE to PE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">5. PE to KE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">6. Positive work (correct) PE (wrong) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">7. Positive work (correct) Both (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">8. Positive work (correct) KE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">9. Negative work (correct) KE (correct) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">10. Positive work (correct) PE (wrong) <span style="font-family: 'Times New Roman',Times,serif; font-size: 120%;">11. Positive work (correct) Both (wrong)