ð Energy ð

Kinetic energy is a form of energy that represents the energy of motion. It is a scalar quantity, which means it has a magnitude but not a direction. It is, therefore, always positive. The kinetic energy, K (or sometimes E_k) is, therefore, defined as:

K = ½mv²

This quantity will always be a non-zero scalar quantity. If the object has a mass and is moving, it will always be positive. It will be zero in the case of a mass less object or an object at rest (zero velocity). The kinetic energy equation, therefore, gives us no information about the direction of the motion, only about the speed.

Potential energy is the stored energy of position. It can be thought of as energy that is “stored” by any physical system. It is called potential because, in its current form, it is not doing any work or causing any change in its surroundings. It does, however, have the potential to be converted to different forms of energy, such as kinetic. The standard unit for measuring such energy is the joule.

When an object is displaced from its original position and there is energy pulling it back to that position, potential energy tends to exist. A ball at the end of a spring, for example, has energy that will be converted to kinetic energy when allowed to return to its original position. A weight held above the ground will, when released, have potential energy as gravity pulls it back to its original position.

One of the major principles of potential energy is the law of conservation of energy, which states that energy can neither be created nor destroyed. The energy expended to lift an object or compress a spring does not simply disappear; it is “stored” as potential energy. It is then released as kinetic energy by a restoring force. The energy input equals the energy output; there is no gain or loss in overall energy. The potential energy, P (or sometimes E_P) is, therefore, defined as:

P = mgh

Д Adding Vector Components Д

 

Vectors	X	Y
A	-11.5	9.6
B	20	N/A
C	N/A	-13

1. Set your Positive Axes.

2. Break all vector down to two components (x and y). To help you keep your thoughts organized, use a graph as shown above.

3. Solve for ∑x and ∑y using the Pythagorean and the trigonometry equations.  

Vector A: 

X = Sin50° x 15km

    = 11.5km

Y= Cos50° x 15km

   = 9.6km

4. Use the Pythagorean to add the two sums of components(∑x and ∑y).

Total

8.5

-3.4

h²=a²+b²

h²=8.5²+3.4²

h²=83.81

h=9km 

5. Use trigonometry to solve for the angle

tanӨ= opp/adj

 = x/y  

      =8.5/3.4

=68°

6. Write your final results.

9 km [S68°E]

Ж Deriving Eq 4 from a Velocity-time Graph Ж

Ψ Deriving Eq 3 from a Velocity-Time Graph Ψ

§ Translation of Motion Time Graph §

Slope

Area

☼ Right Hand Rules ☼

   The Right Hand Rules were created by scientists to help us predict how magnetic forces act. They are called the Right Hand Rules because they involve using your right hand.



Right Hand Rule #1: for conventional current flow. Grasp the conductor with the thumb of the right hand pointing in the direction of conventional, or positive (+),  current flow. The curved fingers point in the direction of the magnetic field around the conductor.



Right Hand Rule #2: for conventional current flow. Grasp the coiled conductor with the right hand such that the curved fingers point in the direction of conventional, o positive (+), current flow. The thumb points in the direction of the magnetic field within the coil. Outside the coil, the thumb represents the north (N) end of the electromagnet produced by the coil.

Right Hand Rule #3: for conventional current flow: The motor principle. open the right hand so that the fingers point in the direction of the magnetic field (from north to south). Rotate the hand so that the thumb points in the direction of conventional (+) current flow. The orientation of the palm indicates the direction of the force produced.

♥ Magnetism and Electromagnetism ♥

17.1 The Magnetic Force -- Another Force at a Distance

      A magnetic field is the distribution of a magnetic force in the region of a magnet. The same theory can be applied to magnets as well as electrostatic forces - With electronic fields, there are two different magnetic characteristics, labeled north and south, that are responsible for magnetic forces. 

THE LAW OF MAGNETIC FORCE : Similar magnetic poles, north and north or south and south, repel one another with a force at a distance. Dissimilar poles, north and south, attract one another with a force at a distance. 

    To map a magnetic field you use a test compass, instead of the test charge we used is electrostatics. 
   The Earth itself acts as a giant permanent magnet, producing its own magnetic field. it is suggested that this magnetic field is produced because of the flow of hot liquid metals inside the Earth. Magnets are also known to attract other materials such as iron, nickel, and cobalt, or mixtures of these three. They are called the ferromagnetic metals. 
DOMAIN THEORY: All large magnets are made up of many smaller and rotatable magnets, called dipoles, which can interact with other dipoles close by. if dipoles line up, then a small magnetic domain is produced. 
17.2 Electromagnets
OESTED'S PRINCIPLE : Charge moving through a conductor produces a circular magnetic field around the conductor. 
    To help us predict how magnetic forces act, scientists have developed several hand signs  called right-hand rules because they involve using your right hand. 
↓  Predicts the direction of the magnetic field around a straight conductor. 
RIGHT-HAND RULE #1 for conventional current flow Gasp the conductor with the thumb of the right hand pointing in the direction of conventional, or positive, current low. The curved fingers point in the direction of the magnetic field around the conductor. 
↓  Predicts the relationship between the direction of convectional current flow in a coil and the direction of the magnetic field at the end of the electromagnet. 
RIGHT-HAND RULE #2 for convectional current flow Grasp the coiled conductor with the right hand such that curved fingers point in the direction of conventional, or positive, current flow. The thumb points in the direction of the magnetic field within the coil. Outside the coil, the thumb represents the north end of the electromagnet produced by the coil. 

♦ Resistance - Ohm's Law ♦

    Resistance is defined as the ability of a substance to prevent or resist the flow of electrical current. We can calculate resistance by measuring the quantities of potential difference across the load and the current passing through it.            


                                    R = V / I            

R is measured in ohms, named after Georg Simon Ohm (1787-1854)
    Mr Ohm found out that the V / I ratio was constant for a particular resistor, and that was the first step in the development of Ohm's Law. 
There are 4 factors that affect Resistance:
          ◘ Length - If the length doubles, so does the resistance.          ◘ Cross-selection area - it the cross-selection is doubled, then the resistance is cut in half.          ◘ Type of material - Since some materials are better than others, if the resistivity (general measure of the resistance of a substance) is doubled, then the resistance is also doubled.           ◘ Temperature - (This only occurs is some substances) If the temperature of the conductor is increased, it usually leads to an increase in the resistance. 
   ○ Kirchhoff's current law states that the total amount of current into a junction point of a circuit equals the total current that flows out of that same junction.     ○ Kirchhoff's voltage law states that the total of all electrical potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop. 

♠ PRELAB: Using Voltmeter and Ammeter♠

Name	Symbol	Unit	Definition
Voltge	V	Volts	Potential difference from any 2 points in circuit.
Current	I	Amperes	Flow of charge.
Resistance	R	Ω	A measure of the opposition to the current flow.
Power	P	Watts	Rate of flow.

Energy Ball Activity

Questions

1. Can you make the energy ball work? What do you think makes the energy ball flash and hum?
2. Why do you have to touch both metal contacts to make the ball work?
3. Will the ball light up if you connect the contacts with any material?
4. Which materials will make the energy ball work? Test your hypothesis. 
5. This ball does not work on certain individual - what could cause this to happen?
6. Can you make the energy ball work with all 5-6 individuals in your group? Will it work with the entire class?
7. What kind of a circuit can you form with one energy ball?
8. Given two balls (combine two groups): Can you create a circuit where both balls light up?
9. What do you think will happen if one person lets go of the other person's hand & why?
10. Does it matter who let's go? Try it.
11. Can you create a circuit where only one ball lights (both balls must be included in the circuit)
12. What is the minimum number of people required to complete this?

Answers

1. Yes you can. 
2. You need to touch both metal contacts to complete the circuit for the ball to work.
3. It depends if the material is a good conductor of electricity or not so no, not all material will work. 
4. Materials like metal, 
5. If the individual were to wear gloves, or a type of material (insulator) that does not conduct electricity very well, or if they were to touch one of the metal contacts with their nail, then they would not be able to make the ball work. 
6. Yes you can. Yes it will.
7. A series circuit.
8. Yes you can.
9. The ball won't hum or flash because the circuit is broken. 
10. It does not matter who let's go. Either way, you are still left with a broken circuit.
11. Yes you can. It is called a parallel circuit. 
12. 1 person. 

Difference Between Parallel and Series Circuit

The series circuit is a single path for current to flow. Like Christmas tree lights, if part of the path is obstructed (a light burnt out) they all go out.

Parallel circuits have more than one path for the current to flow, so if a path is obstructed, the current can take another path (like rungs of a ladder).

Read more: What is difference between parallel and series circuit? | Answerbag http://www.answerbag.com/q_view/794765#ixzz0zGIIJyDV

...Structure?...

              
     As our first day of regular class time, our physics teacher decided to do an activity that involved building a structure using only 5 sheets of newspaper and a roll of tape that was as long as our desks. the goal was that the structure should be as tall as you can make it and at the same time, be stable enough to stand. (And no, taping the end of the structure to the desk was not allowed  .) So anyways...

    ♦ My group (total of 3) decided that what was most important for this structure to be able to stand was for it to have a  good base. One that was bigger than the rest of its body and also strong enough for it to be able to carry the entire weight of the structure. Our base was basically 1 page of the newspaper, folded in half, and folded into the form of a rectangle. (we thought about and tried doing a triangle first but we couldn't figure out how so we just went with the next best thing) what we did next was add 2 more papers (same shape), that were smaller in width (or in this case diameter since our rectangles weren't exactly rectangles) than the one before to make the bottom as strong as possible. On the last one, we pinched the 2 corners, and ended up with a very small hole, just big enough to fit the 2 attached tubes (which we made by rolling up the paper). This added lots of height to our structure but it wasn't until one more thing to it that it ended up being the tallest out of the entire class (out of 8 others). After everything the only thing that was left was a very long strip of paper that we had cut from the previous paper that we used at the beginning. My partner had the smart idea of just folding it in half and just sticking it inside the tube. that added about a good 30cm to the total height of our structure and made us th winning team of the activity!!!                 hehe. 


    ♣ So in the end, we learned that the most important thing to a tall structure is the base and the fact that the higher you go the less weight you need to add to the structure. If you follow this I can guarantee you a  total success in your tower!!! 

BTW. As i was searching through the internet for a picture i found a link to a conversation about the same activity. if you're interested in whats being said here's the link: http://www.physicsforums.com/archive/index.php/t-56925.html

♠ Current Electricity and Electric Circuits ♠

16.2 Current

  
    Electric Current involves electrons repelling one another and passing through a conductor. Ex. The pumping station provides the water with gravitational potential energy, pumping it up into the water tower. the water then later loses this energy as it is piped through the sprinkler and back to its point of origin. the same thing occurs in an electric circuit. The energy source provides electrons with energy and  the electrons are transported by the conductors through the circuit and then back to the source to be re-energized.

   The rate of charge flow can be calculated using this expression:             

             I is the symbol given to calculate the rate of charge flow in amperes (A)
            Q is the charge in coulombs (C)
             t is the time in seconds (s)

                     
    Once upon a time, current flow was believed to move from the positive (+) terminal to the negative (-) terminal on any power supply. it is now well understood that, in actuality, current is a flow of negatively charged electrons repelling one another.to keep track of this, a colored wiring convection is used in which black represents the negative terminal and red represents the positive terminal of any power supply.  



Definitions:
          ♦ Electric Current is the flow of charge.
          ♦ Current is the rate of charge flow.
          ♦ Conventional current is a model of positive charge flow.
          ♦ Direct current or DC is the current flow in a single direction from a power supply through the conductor to a load and back to the power supply.
          ♦ Alternating current or AC occurs when the electrons periodically reverse the direction of their flow.
          ♦ Circuit is the path of the current and is required for any electrical device to work properly.
          ♦ Voltmeter is a device that measures the difference between any two points. (Must be connected in parallel with a load in order to compare the potential)