Different types of energy!!

Everything have different types of energy and there are many energy acting on many object such as, kinetic energy, potential energy, gravitation potential energy, energy, elastic energy, thermal energy, mechanical potential energy, nuclear energy, and chemical energy.


Kinetic Energy→↓
The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest.

Potential energy→↓
Potential energy is one kind of the energy that we learned in our physics class. Potential energy is the energy stored in a body or in a system due to its position in a force field or due to its configuration. We calculate potential energy in J (joule). It's the SI unit of work and energy. The term "potential energy" was coined by the 19th century Scottish engineer and physicist William Rankine.

Gravitation energy→↓
Gravitaion energy is the energy that act on any object in the world due to the gravity. If an object falls from one point to another point inside a gravitational field, the force of gravity will do positive work on the object, and the gravitational potential energy will decrease by the same amount.

Thermal energy→↓
Thermal energy is the energy that makes objects hot. It is a form of kinetic energy at the molecular level, the movements of atoms and molecules. It is the translation of two different energy. For example, Hot water has more kinetic energy then cold water because there are more molecule acting in the hot water than the cold water.

Elastic energy→↓

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.



Chemical Energy→↓

  Chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances. Breaking or making of chemical bonds involves energy, which may be either absorbed or evolved from a chemical system.



CANNON!

To make the best cannon, it's back to the projectile moetion problems, cannon is highly related to the projectile motion. To make a better cannon, we should have a good angle and the inside of the cannon should have less friction, so the deceleration would be less. Although we are not using the gunpowder in our experiment, but we could use alcohol so the power would be less and it would be more safe to do the experiment. In this experiment, the force that's acting on our cannon ball would apply to Newton's first law and it might travel 1~ 4m. As there a velocity on the cannon ball causes by the cannon, it would turn up to be the concert of projectile motion. Best way to make the angle of the cannon is between 40 to 50 degree.

Newton's Problems

 There are four kinds of Newton's problems that we learned in our physics class, those four are equilibrium, incline, pulley, and train.

Equilibrium happens when there are no acceleration acting on the object and the positive force are equal to the negative force.

Assumptions→↓
 -no air resistance
- no acceleration  ax = 0   ay = 0
- T1y = T2y = mg
-one free body diagram
-Set positive axises

The second Newton's problem is incline. There are two different types of incline, static and kinetic.

Incline (static)

Assumptions→↓

-no air resistance

-no acceleration
-Fn is perpendicular to the surface

-Fgy - Fn = 0
-one free body diagram

The only different between static incline and kinetic incline is the change of acceleration. In kinetic incline, there is acceleration.

Assumptions→↓

- no air resistance

-Acceleration not = 0

-positive in the direction of acceleration
-Fn is perpendicular to the surface
-one free body diagram
-Fn - mgy = 0

Pulley

Assumptions→↓

-pulley is frictionless

-rope frictionless

-no air resistance

-2systems>2 FBDs

-T1 = T2

-a of the system is the same

-positive in the direction of acceleration



Train

Assumptions→↓

-positive in direction of acceleration

-3 FBDs

-no air resistance

-cables weightless

-a is consistant

 

Projectile Motion!

To calculate a projectile motion problem, initial velocity, final velocity, accerleration, time, and distance are included, but the mass of the object is excluded. The key to solve the projectile motion problems is to break in two components, the horizontal and vertical component.

As we know that the gravitational acceleration is 9.8m/s². The acceleration in the y-component is always 9.8. If the speed of the obeject would be constant in the x-component. As we know that the speed acting on the object is just begin, the initial velocity/ the highest point of the object in y-component would be 0.

There are 4 types of projectile motion, the first type would be an object from the top and a force acting on the horizontal component. This kind of projectile motion can be solved by determining the time. In this case, the initial velocity of y-component is always zero and the velocity in x-component is always constant.

※The first type of projectile motion

The second type of the proejectile motion would be an object that has a velocity against the gravity. In the highest point of the whole projectile system, the velocity would become zero and the acceleration is determined as negative 9.8.

The third type of projectile motion also would be an object that have a velocity that against the gravity. But in this case, the displacement in y-component is not zero any more, there would an positive number in the y-component.

The last type of projectile motion is an object that habe a velocity that against the gravity and end with a negative displacement in the y-component.



PHYSICS BEHIND ROLLAR COASTER

  I go to wonderland often because of the rollar coaster. I am a really big fan of rollar coaster, but I haven't known about the physics behind rolllar coaster before the physics class.

  The physics in the rollar coaster is due to the gravitational force and the apply force acting on it. The friction in the rollar coaster is also an very important part of a rollar coaster. Without friction, the rollar coaster might not able to stop and the people wouldn't be able to step forward. Anthor physics behind rollar coaster is the energy of the collar coaster. As we know, Many energy in acting on an obect, the most affective energy that act on the collar coaster would be potential energy and the kinetic energy. As the rollar coaster is pulled on the top, a porential energy is created and once the rollar rolls from the top, the potential energy would transferred to both kinetic and potential energy.

How to add vertors

To determine the resultant : As we add straight vectors (※subtracting vectors means adding a vector in the opposite direction) , we would find the closest distance between the origin and destination. That would be our resultant. According to the Pythagorean Theorem, a² + b² = c², which "c" represents the hypoteneuse.

To determine the angle : The easiest way to measure the angle accordance to N or S is to use the protactor. But in this course, we would recommand to use the Trigonometry Theorem, Cos, Sin and Tan.

 To determine the vectors components: First, we set the positive axes, then break all vectors down into two components ( x and y). We calculate the total of x and y and follow the step as above (To determine the resultant, To determine the angle )

How equation#4 derived from the V/T graph

In Equation #4, only V2 is usable. In another way to calculate the area of the trapezoid, we could calculate the area of the trangle and subtract the area of the triangle.   That would come out the equation #4, which is d=V2Δt-½aΔt².

Equation #4  ────  d=V2Δt - ½aΔt²
                                   ↓            ↓
                              Rectangle    Triangle


To determine the area of the rectangle, we would multiple V2 (as symbol "b" shown in the graph《Height》)  to t2 - t1, which known as Δt. (as symbol "h" shown in the graph《Height》)

It will give us an equation,
Area of Rectangle = V2Δt

To determine the area of the rectangle, we would multiple (V2 - V1) 《Base》to  Δt 《Height》divided by 2.

According to Equation #1  = V2 - V1, so, as we sub this equation,
                                         V1= V2 -  aΔt

Area of triangle = ½(V2 - V1)(Δt)
Area of triangle = ½(V2 - V2 - aΔt)Δt
Area of triangle = ½(- aΔt)Δt
Area of triangle = -½aΔt²

Displacement = Area of rectangle - Area of triangle (As we sub the equations in,)

Displacement = V2t + ( -½aΔt²)

Displacement = V2t - ½aΔt²

How equation #3 translates into the v/t graph

                               
Equation #3  ────   d = V1Δt + 1/2 aΔt²
                                          ↓             ↓
                                   rectangle   triangle

As the graph above, we know that we have to calculate the area of the trapezoid to find out the displacement. But, in Equation #3, only V1 is usable. We would break down the trapezoid into a triangle and rectangle.

To determine the area of the rectangle, we would multiple V1 (as symbol "a" shown in the graph《Width》) to t2 - t1, which known as Δt. (as symbol "h" shown in the graph《Height》)

It will give us a equation of  Area of rectangle = V1Δt

To determine the area of the triangle, we would multiple (V2 - V1) 《Base》to  Δt 《Height》divided by 2

According to Equation #1 aΔt = V2 - V1, so, as we sub this equation,
Area of triangle = ½(V2 - V1)(Δt)
Area of triangle = ½aΔt(Δt)
                        
Displacement = Total Area

Displacement = Area of rectangle + Area of triangle  (As we sub the equations in,)

Displacement = ½V1Δt + aΔt²
                                      

Translation of Graph

Graph B)
There are five sections in this graph:

Velocity →↓
Section 1) Time (in second) 0 ~ 1  : The Velocity starts at the x-axis, a horizontal line which lies on the x-axis is created.
Section 2) Time (in second) 1 ~ 3  : A horizontal line is created in the positive area at  0.75 as the walking speed is 0.75m/s [E]     Slope: 1.5(m)/2(s)
Section 3) Time (in second) 3 ~ 6  : No change in distance, so there's a horizontal line on the x-axis.
Section 4) Time (in seond) 6 ~ 7.5  : A horizontal line is created in the negative area at -0.53 as the walking speed is 0.53m/s [W]c or -0.53m/s [E]    Slope: -0.8(m)/1.5(s)
Section 5) Time (in second) 7.5 ~ 10  : No change in distance, so there's a horizontal line on the x-axis.

Acceleration →↓
 There's no acceleration in this graph. The line lies on the x-axis.

Graph C)
There are 5 sections in this graph
Velocity →↓
Section 1) Time (in second) 0 ~ 3  : A horizontal line is created in the negative area at -0.5 as the walking speed is 0.5m/s [W] or -0.5m/s[E]   Slope: -1.5(m)/3(s)
Section 2) Time (in second) 3 ~ 4  : No change in distance, so there's a horizontal line on the x-axis.
Section 3) Time (in second) 4 ~ 5  : A horizontal line is created in the negative area at 1 as the walking speed is 1m/s [W] or -1m/s [E]    Slope: -1(m)/1(s)
Section 4) Time (in second) 5 ~ 7  : No change in distance, so there's a horizontal line on the x-axis.
Section 5) Time (in second) 7 ~ 10  : A horizontal line is created in the positive area at 0.83 as the walking speed is 0.83m/s    Slope: 2.5(m)/3(s)

Acceleration →↓
There's no accelerationin this graph. The line lies on the x-axis.


Graph D)
There are 4 sections is this graph:

Distance →↓
Section 1) Time (in second) 0 ~ 2  : The distance start from 0m, and stay for 2 seconds therefore a horizontal line lies on the x-axis.
Section 2) Time (in second) 2 ~ 5  : The line goes up with a positive direction and stop at 1.5m away the origin.  Distance: 0.5(m/s)*3(s)
Section 3) Time (in second) 5 ~ 7  : The velocity is 0, that causes a horizontal line is drawn at 1.5m.
Section 4) Time (in second) 7 ~10  : The line decreases with a negative direction and stop at 0. Distance : -0.5(m/s)*3(s)
Acceleration →↓There's no acceleration in this graph. The line lies on the x-axis.


Graph E)
There are 4 sections in this graph:

Distance →↓
Section 1)
 Time (in second) 1 ~ 4  : The speed increases in a speed of 0.125m/s Slope: 0.5(m/s)/4(s), so it will become a curve, a cureve which has a smaller slope at first and become gather and the line stop at 1m away the origin.
Section 2) Time (in second) 4 ~ 6  : The line goes up with a positive direction and stop at 2m away the origin.   Distance: 0.5(m/s)*2(s)
Section 3) Time (in second) 6 ~ 9  : The line decreases with a negative direction and stop at 0.8m away thre origin.  Distance: -0.4(m/s)*3(s)
Section 4) Time (in second) 9 ~ 10  : The velocity is 0, that causes a horizontal line is drawn at 0.8m

Acceleration →↓Section 1) Time (in second) 1 ~ 4  : A horizontal line is created at 0.125(m/s2) Slope: 0.5(m/s)/4(s).
Section 2 ~ 4) There're no acceleration in section 2 to 4. The line from 4 to 10 second is on the x-axis.

Graph F)
There are 3 sections in this graph:

Velocity →↓
Section 1) Time (in second) 1 ~ 4  : A horizontal line is created in the positive area at 0.26m as the walking speed is 0.26m/s  Slope: 0.9(m)/3.5(s)
Section 2) Time (in second) 4 ~ 6.5  : No change in the distance, so there's a horizontal line on the x-axis.
Section 3) Time (in second) 6.5 ~ 10  : A horizontal line is created in the positive area at 0.43 as the walking speed is 0.43m/s  Slope: 1.5(m)/3.5(s)
Acceleration →↓There's no acceleration in this graph. The line lies on the x-axis.

Motion prelab

Distance (m) VS. Time (s)

1. Stay at 1m away from the origin for 1 second.

2. Walk 1.5m in 2 seconds away from the origin. [0.75m/s]

3. Stay at 2.5m away the origin for 3 seconds.

4. Walk 0.75m in 1.5 seconds towards the origin. [0.5m/s]
5. Stay at  1.75m away teh origin for 2.5 s.

                                             Distance (m) VS. Time (s)

1. Start from 3m away the origin, walk 1.5m for 3s towards the origin. [0.5 m/s]

2. Stay at 1.5m away the origin for 1 s.

3. Run 1m in 1 second toward the origin. [1 m/s]

4. Stay at  0.5m away the origin for 2 s.

5. Run 2.5m away the origin in 3 seconds. [0.83 m/s]

                                Velocity

1. Stay for 2 seconds.
2. Walk at 0.5 m/s away the origin for 3 seconds.
3. Stay for 2 seconds.
4. Walk at 0.5 m/s toward the origin for 3 seconds.








                                                                                  Velocity

 

1. Speeds up  to 0.5 m/s away the origin in 4 seconds.

2. Walk in constant speed [0.5m/s] away the origin for 2 seconds.

3. Walk at [0.4 m/s] towards the origin  for 3 seconds.

4. Stop walking and stay for 1 second.



                    Distance (m) VS. Time (s)

1. Start from 0.9m away the origin, walk  0.9m away the away in 3.5 s [0.26 m/s]

2. Stay at 1.8m away the origin for 3 s.

3. Walk 1.5m away the origin in 3.5 s (0.43 m/s)







                                                                                        Velocity

1. Walk  at 0.35 m/s away the origin for 3 seconds.

2. Walk at 0.35 m/s toward the origin for 3.5 seconds.

3. Stand  for 3.5 seconds.

MOTOR PRINCIPLE

 1.     In this motor model, the power (conventional
current flow) flow though the brushes and connect to
the commutator pin. It causes it to become a DC motor.
According to the RHR #2, the direction of conventional
current flow is shown in the picture which located at the
middle. After using the RHR #2, we could predict the
direction of the force by using the RHR #3. The direction
of the force at the left side is different from the right
side’s, so the cork could spin.

.

 2.     Then, after the motor spins half way of a circle, the
commutator pins touched another brush (not the brush
 that has been touched before the motor spins) that
changed the direction if the current and also the direction
of forces changed, too.

 
3.     After the forces changed when the motor reached
the half way point, the motor continues to spin and
it changed its forces while it meets another half way
point, and it spins more and more that forms a loop.

 

Now， the loop has been formed and the cork can spin
nicely until there is no power anymore.

RHR 1&2

The right hand rule helps demonstrate the relationship between conductor current and the direction of force. The first right hand rule for convertional current flow is used to determine the direction of current flow in a conductor. The conductor where you right hand's thumb is pointing at, is the direction of convertional. (positive current flow).

In the second right hand rule, the propose is to determine the direction of the magnetic field. The thumb point at the North -Pole.  

Notes - Magnetism p.582~589

● Magnetic Field is the repartion of a magnetic force in a region of a magnet.

●We use test compass to measure the magnetic forces within an area or object, instead of the test charge we used in electrostatics.

●Magnet attracts ferrous objects such as, pieces of iron, steel, nickel and cobalt.

●The magnet repel one another if both magnetic poles are north and north, or south and south ; The magnet attract one another if magnectic poles are difference(dissimilar). <North and South>

●The Domin Theory tells us that all large magnet are constitute by many smaller and rotatable magnet. Those small and rotatable magents are called dipoles. Dipoles can interact with other dipoles to close by.

● Magnetic Domin is created if dipoles are lined up.

●Oersted’s Principle is an important discovery made by Hans Christian Oersted. Oersted’s Principle tells that a circular magnetic field around the conductor is produced when charge moving through a conductor.

●There are two right- hand rules that help us to predict how magnetic force act. Right- hand rules are like physical formula because they allow us to take certain known factors and predict one unknown factor.

●The first right hand rule for convertional current flow is used to determine the direction of current flow in a conductor. The conductor where you right hand's thumb is pointing at, is the direction of convertional. (positive current flow).


●The second Right hand rule is to determine the direction of current flow within a coiled. The thumb point at the direction of the magnetic field within thr coil.

Notes from p.553~563

◎Electrical resistance is a material's opposition to the flow of electric current and it's measured in Ohms (Ω)

◎ Circuit with a boarder pathway and narrow pathway is different by the current flow, there're more current pass though a circuit with a boarder pathway than a circuit with a narrow pathway

◎The resistance of a conductor depends on things such as, its length, cross-sectional area, the material it is made of , and its temperature.

◎Series circuit is the circuit which the loads are connected one after another in a single path.

◎If two or more components are connected in parallel they have the same potential difference across their ends, that's parallel circuit and they are side by side.

←◎Georg Simon Ohm is the person  who discovered that V/I ratio was constant for a particular resistor. (Known as the Ohm's law)

◎ Kirchhoff's Current Flow us the total amount of current into a  junction point of a circuit equals the total current that flows out of that same junction.
 
             I(1) + I(2) + I(3) = I(T) = I(4) + I(5)

◎    Kirchhoff's Voltage Law is the total of all electrical potential decreases in any complete loop is equal to any potential increases in that circuit loop.                                             
                                                             Gustav Robert Kirchhoff →↑

◎There is no net gain or loss of electric charge or energy in any circuit with the laws of conservation of electric charge and the conservation of energy, these laws are corresponding to the Kichhoff's laws too.

※ R = Resistance   V = Volts (The potential Difference)  I = Amperes (Current flow)

The equation of calculating electrical resistance is                        

R = V/I                                                            

               

The equation of calculating voltage (volt) is
                                                                                                    V = IR


The equation of calculating Current flow (Amperes) is
                             I = V/R

The Prelab Table

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Energy ball activity - Question 1 to 12

※Can you make the energy ball work? What do you think makes the ball flash & hum?  
    YES,  we made the ball flash and hum by being part of the curcuit. We are the conductor(wires) and the ball is the resistance(light).

※Why do you have to touch both metal contacts to make the ball work?
 
    We become the conductor, the elctrons flow thougth in our body  and that's called "current flow". We have to touch both sides to make the circuit completed.

※Will the ball light up if you connect the contacts with any material?
  
    No, the ball won't light up with any material except conductor.
※Which materials will make the energy ball work?
 
    I thick that metals could make the ball works because metals are conductor, the electrons could flow thougth it.

※This ball does not work on certain individual. What could cause this to happen?
 
   I think the current flow only work with people who have moisture skin. People who with dry skin can't make the electrons pass thougth their body.
※Can you make the energy ball work with all 5-6 individuals in your group? Will it work with the entire class?

    Yes, it works with any number of people, the size of the circuit will be bigger if more people become part of the circuit.

※What kind of a circuit can you form with one energy ball?

    We can form the simple circuit with on energy ball. The electrons transfer thougth our body.

Energy ball : light
Group members : conductor

※Given two balls, can you create a circuit where both balls light up?
     Yes, it's possible to create a circuit with both balls light up, the name of the circuit is series circuit.
  

※What do you think will happen is one person lets go of the other person's hand and why?

   The current flow will stop and the ball won't light up. It just like the switch of  a simple circuit, one person lets go means that the circuit is not completed, so the electrons can't flow thougth the conductor.

※Does it matter who lets go?

   No, the current flow stops if anyone lets go in a simple circuit. It only matters who lets go in paralel circuit.

※Can you create a circuit where only one ball lights (both balls must be included in the circuit)？

   We can create a parallel circuit to make only one ball lights. As you can see in the picture below, the electricity can still suppy to the other light bulb if one is off.

※What is the minimum number of people required to complete this?
   I think one person is already possible to complete this.

Difference between series circuit and parallel circuit

 Series circuit is the circuit which the loads are connected one after another in a single path. If two or more components are connected in parallel they have the same potential difference across their ends, that's parallel circuit. The difference between series circuit and parallel circuit is that a parallel circuit has more than one path in the circuit, and a series circuit only has one way around it.

For additional information, you can watch the vedio below.

※Physics Tall Structure Challenge

                                                                           §The Physics of tall structures

"Higher the structure, lighter the top" The base of a tall structure should be wide and heavy, so it can support the weight on the top. The centre of gravity also has to be low. If the centre of gravity is to high, the structure might fall at any time.









§What makes a tall structure stable?

 The base of a tall structure is the most important part for the structure's stability. For example, while we are playing JENGA, what will happen if most of the blocks at the bottom are removed and what will happen if more and more blocks are put on the top?

                                      "It will fall"

So, a tall structure must have a wide and heavy base to secure the whole structure.

§What is the centre of gravity?
The centre of gravity (CP) is the average location of the weight of an object, it's equal to the center of mass.