Energy

Sound energy:  
           Sound energy travel through media, such as gas liquid or solid, the energy produced by sound vibrations.

Thermal energy:
           In the other word is heat. The sum of potential energy and kinetic energy, in random motion of particles of a material.

Gravitational potential energy is energy an object possesses because of its position in a gravitational field. The most common use of gravitational potential energy is for an object near the surface of the Earth where the gravitational acceleration can be assumed to be constant at about 9.8 m/s²

. Elastic energy is the potential mechanical energy stored in the configuration of a material or physical system as work is performed to distort its volume or shape.

mechanical energy describes the sum of potential energy and kinetic energy present in the components of a mechanical system. Mechanical energy is the energy associated with the motion or position of an object.

Chemical potential energy：

Chemical potential energy is a form of potential energy related to the structural arrangement of atoms or molecules.

cannon

 A cannon works very similar to a gun works. A charge is loaded into the cannon (such as gunpowder) and then the cannonball is loaded in on top of the charge. Wadding is placed into the top of the cannon along with the fuse. The fuse is lit which sets the wadding on fire which in turn ignites the charge. The gases from the charge will rapidly expand causing the cannon ball to fly from the end of the cannon.

Equilibrium

• no friction
• a=0.....ax=0   ay=0

Inclines (Static)

• fs=mFN
• a=0
• +in direction of a
•  no air resistance
• m=tan(angle)

Inclines (Kinetic)

• fk=mFN
• +in direction of a
•  no air resistance
• ay=0

Pulleyès

• frictionless palleys trope
• no air resistance
• multiple FBD
• + in direction of a
• T1=T2
• a of system is the same

Trainès

• 1FBD for 2
• 3FBD for T1,T2
• ay=0
• a is resistant
• no air resistance
• + in direction of a

Eq#3     d = V1Δt + 1/2aΔt^2

we can know from the groph:

aΔt = V2-V1

Δabc----d2 = V1 Δt

Raceo-----d1 =1/2 (V2-V1) Δt

d = d1 + d2

    =V1 Δt + 1/2 (V2-V1) Δt

    =V1 Δt + 1/2 (aΔt) Δt

    =V1 Δt + 1/2aΔt^2

Eq#4   d= V2 Δt – ½ a Δt^2

we can know from the graph:

Δabd------d1 = (V1+V1) Δt

Rbdoe----d2 = V2Δt

d = V2Δt - (V1+ V2) Δt  

   = V2Δt - ½ a Δt^2

THE MOTOR REPORT

The materials we used to build the motor are: wood, nail(four long, four short), cork(cylinder), stack(axed), paper clips, thumbtacks(pin), pop can, and sand paper.

First we placed the four inch nails. The length between each two nails on the both side is two to three cm, and the space between each pairs is five to six cm. we hammered the nails onto the wood. Then we places pin through the centre of the cork. On the one end of the cork we placed two pins, they are the commutators. Then we warp the wire around the cork. We bare both ends of the wire and wrap the bared section around both of the pins. We cut the pop can into two pieces, hammered them into wood on the both side of the commutators pin. We also sanded both side of the pop can pieces, we used it as the brushes. put he magnets on the nails, with opposite facing each other.(1)

When connect with the power, the motor turned round 360 degrees, more than three times.

If there are on brushes the motor can’t turn three times, it will stop. The current must be swish. The two brushes are used to swish the current. Without the brushes, if one of the wires goes to the top, the motor will be stopped, because the magnetic field on the wire are going two different ways. With the brushes helping swish current, so the magnetic field on the wire can also be swished. So the motor can be turn around more than three times.

From the project, team work and organization is very important. A good team work and organize effect on the result good or not. To do the better work also depend on the prepare work.

Right hand rule:

• 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.

• Grasp the 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 coil.

Magnetic

• A magnetic field is the distribution of a magnetic force in the region of a magnet.
• As with electric fields, there are two different magnetic characteristics, labelled north and south.
• Metals like iron, nickel, and cobalt, or mixtures of these three are called the ferromagnetic metals.
• Earth acts like a giant permanent magnet, producing its own magnetic field.
• Lifting electromagnet, relay, electric bell are the uses of electromagnets.
• 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.
• Oersted's principle: charge moving through a conductor produces a circular magnetic field around the conductor.

Right hand rule:

• 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.
• Grasp the 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 coil.

Text book P553-P563 notes taking

1. The measure of this opposition to flow is called electrical resistance.
2. R=V/ I  R is the resistance in volts/ ampere, given the derived unit of ohm.
3. V/I ratio was constant for a particular resistor. this ratio is called Ohm's law.
4.---the larger the conductor the greater the resistance.
   ---the larger the cross-sectional area of the conductor, the less resistant it has to change flow.
   ---the type of the material--some materials are better conductor than others.
   ---higher temperatures tends to increase the resistance.
5. A wire that has a small gauge number has a large cross-sectional area. A small cross-section has a large   gauge number.
6. A series circuit the loads are connected one after another is single path.
7. A parallel circuit the loads are connected side by side.
8. Kirchhoff's current law: the total amount of current into a junction point of a circuit equals the total current that flows out of that same junction.
9. Kirchhoff's voltage law: the total of all electrical decreases in any complete circuit loop is equal to any potential increases in that circuit loop.
10. ---in series circuit------IT=I1=I2=I3
                                                       VT=V1+V2+V3
                                                        RT=R1+R2+R3
        ------in parallel circuit------IT=I1+I2+I3
                                                          VT=V1=V2=V3
                                                          1/RT=1/R1+1/R2+1/R3

Name                         Symbol           Unit          Definition

Potential different         V                V (volt)     The electrical potential energy for    
                                                                                  each coulomb of charge.
______________________________________________________________

Current                        I                 A(ampere)       The rate of charge flow.

______________________________________________________________

Resistance                   R               ohm                 The opposition to current flow.

______________________________________________________________

  Power                      P              W(watts)      The rate at which electrical energy
                                                                    is passed on the various circuit load.
______________________________________________________________
                                                                                                  .            

Parallel and Series Circuit

What is the different between a parallel and series circuit?

In a series circuit the loads are connected one after another in a single path

In a parallel circuit loads are connected are side by side

 

Question 1-12 of energy ball

1.Can you make the energy ball work? What do you think makes the ball flash and hum?
   Yes we can make the energy ball work.  We touch both metal contacts complete the circuit, there is     current go though the energy ball, so the ball can flash and hum.
2. Why do you have to touch both metal contacts to make the ball work?
   We have to touch both metal contacts to complete the circuit, make the ball work.
3. Will the ball light up if you connect the contacts with any material?
    No, the ball will not light up with any material except conductors such as metal and water...
4.Which materials will make the energy ball work?
  Conductors, for example, metal, water, ourselves...
5.This ball does not work on certain individual, what could cause this to happen?
  When the skin is very dry this ball does not work.
6.Can you make the energy ball work with 5-6 individuals in your group? Will it work with the entire class?
   Yes, and it works with the entire class.
7.What kind of a circuit can you form with one energy ball?
   I can form simple circuit with one energy ball.
8.Given two balls, can you create a circuit where both balls light up?
  Yes we can.
9.What do you think will happen if one person lets go of the other person's hand and why?
   The ball will not light up, because the circuit is opened, no current go though the energy ball.
10.Does it matter who let's go?

     No, it does not matter
11.Can you create a circuit where only one ball lights up (both balls must be included in the circuit)？
    Yes, form a series circuit.
12.What is the minimum number of people required to complete this?
    At least five people required to complete this.

Struchure challenge.

What make a tall structure stable?

• make the top skinny and the base wide
• the base must be heavier then the top
• the centre of gravity need to be lower
• need more support point

Centre of gravity :  is the average of the weight of an object.  For every object the weight  acts through the center of gravity. Centre of gravity is very important for the flying objects.

Notes on current electricity

• Electrons in a static state have energy.
• Current (I) is the total amount of charge (Q) moving past a point in a conductor divided by the time taken. I=Q/T
• Current flow was thought to move from the positive terminal to the negative terminal.
• An ammeter mus be wired so that all current flows through it.
• Direct current, like a light bulb or other device uses energy.
• V=E/Q    electric potential difference\voltage (v)   increase the electric (E)
• E=VIT
• Potential difference between any two points can be measured using a voltmeter.
• A voltmeter must be connected in parallel with a load.
• The voltmeter must have a large resistance.