Blog 13: CANNONS

Today, Mr. Chung introduced us to a new assignment: CANNONS!

Our main goal is to create a cannon that would shoot the cannonball as far as possible.
In physics terms, we need to build a cannon that would produce the greatest range in the x-axis.

The main factor that determines how far it will go is the angle. A longer barrel would be better because the energy would be applied for a longer period of time; however, it wouldn't work like this for our cannons because our cannonballs are not starting from all the way inside it.

We are only allowed to use 5 pop cans and duct tape. The cannonball is to be made of 2 styrofoam cups tape together to form a closed "cylinder".

Blog 12: Dynamics

In the dynamics unit, there are four major topics: Equilibrium, inclines, pulleys and trains.

Equilibrium 

      In an equilibrium, the forces cancel each other out to make everything equal. In simpler terms, nothing moves when there is equilibrium.

Equlibrium problem

Inclines

     There are two kind of incline problems: Kinetic and static. In an incline, there is friction as the object slides down or as it begins to slide down.               

                                         

Incline problem



Pulleys

Assumptions:

• set your positives (+ in direction of acceleration)
• no air resistance
• T₁ = T₂
• 2 systems - 2 FBDs
• acceleration of both systems are same  

Pulleys problem part 1



Pulleys problem part 2

Trains

Assumptions:

• no air resistance
• set your positives (+ in direction of acceleration)
• no acceleration in y direction
• cords (between the cars) are weightless
• # of FBDs is equal to number of masses



Train problem part 1



Train problem part 2



You should always write the assumptions, as soon as you draw your FBDs



Blog 11: PROJECTILE MOTION

What is projectile motion or parabolic motion?

Any body that is given initial velocity and then follows a path determined by the effect of the gravitational acceleration and by air resistance (air resistance is usually neglected in physics because we want to make it easier to calculate everything)

This image shows an example of a parabolic motion/projectile motion

Gravity (g or sometimes a_g) is always set to 9.81m/s² on Earth

Without the effects of gravity and air resistance, an object would be able to move forever without stopping unless it bumps into something.

Big 5 Equations

          Although the big 5 equations were first used for linear problems, we started to use these for projectile motion. Acceleration is always assumed as 9.81m/s² unless another acceleration is given. 

          The velocities are split into x-components and y-components. In parabolic motion, the x-component is the same throughout, i.e if it started with a velocity of 2m/s it will end with a final velocity of 2m/s. However, this is not the case for the y-component as the gravity gives the object acceleration. This acceleration means that the velocity will be either increasing or decreasing depending on the direction that the object is traveling in. Going up would slow it down and vice versa. Therefore, when the object is going down, the y-component will increase as will the displacement.

      

Blog 10: ROLLERCOASTERS~

Today, we were given our ISUs (Independent Study Units). One of the assignments was to build a rollercoaster, that would be entered into the annual competition at Paramount Canada's Wonderland. This assignment will be a long, difficult one and it will be due on January.

Here is my favourite coaster:

This rollercoaster won for the Artistic Category in 2009

Blog 9: Adding or Subtracting Vectors

There are two main ways to go about adding or subtracting vectors:

1. Use a scale diagram

a) Measure and draw vectors in scale (1cm=1km)
b) Connect the head to tail
c) Resultant is always origin to destination (AYJackson to PMall :P)
d) When you "subtract" vectors, you are actually adding in the opposite direction (12km[N] can be rewritten as -12km[S])

e) Use a protractor to measure the angle in accordance to North and South.

2. Add or subtract by components

a) Set you positive axes

b) Break all vectors into two components (x and y)

c) Solve for ∑x and ∑y (summation of x and y)

d) Use Pythagorean Theorem to add the two sums of components (∑x and ∑y)

e) Use trigonometry to solve for angle

        SOH → sinθ = opp/hyp

        CAH → cosθ = adj/hyp

        TOA → tanθ = sinθ/cosθ = opp/adj

Blog 8: Position-Time & Velocity-Time Graphs

Position vs Time Graphs

Stayed for 1 second at a distance of 1m

Walked away for 2.5 m in 2 seconds 

Stayed at 2.5 m for 3 seconds

Walked approximately 1 m towards in 1.5 seconds 

Stayed for 2.5 seconds at 1.5 m

Walked towards 1.5 m from 3 m for 3 seconds

Stayed for 1 second

Walked towards 1 m for 1 second

Stayed for 2 seconds 

Walked away 2.5 m for 3 seconds

Walked away 1 m for 3.5 seconds

Stayed for 3 seconds

Walked away 1.4 m for 3.5 seconds

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Velocity vs Time Graphs

Stayed for 2 seconds 

Walked towards at 0.5m/s for 3 seconds

Stayed for 2 seconds 

Walked backwards at 0.5m/s for 3 seconds

Speed up from 0 m/s to 0.5m/s for 4 seconds 

Walked at 0.5m/s for 2 seconds

Walked backwards at 0.4m/s for 3 seconds

Stayed for 1 second

Walked at 0.36 m/s for 3 seconds 

Walked backwards at 0.4m/s for approximately 3.75 seconds 

Stayed for approximately 3 seconds

Blog 7: Building an Electric Motor

               On Wednesday, Mr. Chung gave an interesting assignment to the class: We were to create our own electric motors. He asked us to bring our own materials if we could.

Materials:

·         paper clips

·         cork

·         pop can

·         sandpaper

·         thumbtacks

·         stick (axel)

·         nails

·         pins (commutator)

·         scissors

Mr. Chung provided us with most of the materials, including a hammer. He gave us short instructions and hints throughout the lab, such as how the coils should be in parallel to the nails, not perpendicular. If you were to coil them perpendicular

This lab was very effective, for me anyway, because it was a hands-on activity. I got much more out of it then I would have from listening to how it works.

Eddie and I completed our electric motor and presented it to Mr. Chung. He hooked the two pop can sheets (brushes) with 2 wires, which were connected to a large battery. He switched the power source on and our cork started turning very quickly, only slowing down once every few seconds.

On Friday, we took our motor for another spin so we could film it, but it didn’t work as well as the day before. It still worked though…

Here is our video of the motor:     

Blog 6: Magnetism and Electromagnetism

17.1

A magnetic field is the distribution of a magnetic force around a magnet.

• north and south are magnetic characteristics in electric fields
• similar poles repel (north and north or south and south)
• opposite poles attract (north and south)
• a test compass can be used to design a magnetic field
• the general direction is from the north end to the south
 




• 
  
  to test this out, you can sprinkle iron fillings around the magnet, which will form in a circular shape like shown above
• 
  
  Earth acts like a giant, permanent magnet which produces its own magnetic field

A Bunch of Terms

Ferromagnetic metals - metals such as iron, nickel, cobalt, or mixtures of these three that attract magnets.

Dipoles - small rotating magnets that make up large magnets.

 

Magnetic Induction - the ability of ferromagnetic materials to be magnetized

Demagnetization - loss of magnetic strength in a ferromagnetic material

Reverse magnetization - reversal of the polarity of a magnet

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Oersted's Principle states that charge moving through a conductor produces a circular magnetic field around the conductor



Blog 5: Resistance --- Ohm's Law

Section 16.5

Resistance is the measure of opposition to the flow of current

The amount of current flow in a circuit (amount of energy transferred) depends on two factors:

1. 
   
   The potential difference or voltage of the power supply, such as a battery.
2. 
   
   Natural path through the load.

Formula: R = V / I

• 
  
  R is resistance in Ohms (Ω)
• 
  
  V is the potential difference (V or Volts)
• 
  
  I is the current (A or Amperes)

• longer conductors have greater resistance
• thinner wires have greater resistance than thicker wires
• larger cross-sectional area means less resistance
• "resistance of 1Ω when 1A of current flows with a potential difference of 1V across a resistor"

Resistivity is the resistance of a substance (Units: Ω x m).

Gauge number of a wire indicates its cross-sectional area.

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Resistance in Series and Parallel Circuits

Section 16.6

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."

• Kirchhoff's Voltage Law: V_T = V₁ + V₂+ V₃  
• Kirchhoff's Current Law:  I_T = I₁ = I₂ = I₃

 



  

Blog 4: Prelab- Using Voltmeter and Ammeter (Table)

Blog 3: Energy Ball Experiment and Circuits

           On Friday, the class received a new hands-on experiment: We were given "ping-pong balls" that could light up and hum; the balls could do these two things if the circuit was completed. 12 questions were given to us to complete:


1. Can you make the energy ball work? What do you think makes the ball flash and hum?
Everyone in the group was able to make the energy ball work by touching both of the metals on the ball. The ball flashes and hums because we were completing the circuit or creating a closed circuit, which allowed the electrons to move constantly.

2. Why do you have to touch both metal contacts to make the ball work?
Both metal contacts have to be touched by the same person to make the ball work because the circuit has to be closed in order for the electrons to flow. If two people touch one metal contact each without linking their bodies in any way, (such as touching fingers) the ball wouldn't flash and hum.

3. Will the ball light up if you connect the contacts with any other material?
As long as the metal contacts are connected with conductors or semi-conductors and are enclosed in a complete circuit, the ball will flash and hum. Our group tested this out by using a 2 metal balls, which worked and a plastic pen, which did not work.

4. Which materials will make the energy ball work?
As stated before, conductors and semi-conductors would make the energy ball work. Metals would work the best because they have low resistance qualities and have high levels of electrical conductivity.

5. This ball does not work on certain individuals. What could cause this to happen?
This ball does not work on individuals with skins that are not moist enough. Dry skin is a poor conductor of electricity.

6. Can the ball work with 5-6 people or the entire class?
The ball flashes and hums with our whole group and the entire class as long as everyone kept physical contact. (As long as everyone was touching each other's pinkies)

7. What kind of circuit can you form with one energy ball?

With one energy ball, we could form a series circuit.

A schematic of a series circuit

8. Give two balls, can you create a circuit where both balls light up?

Our group joined with another group to experiment this; when we made a complete circuit both balls lit up.

9. What do you think will happen if one person lets go of the other person's hand and why?

If one person lets go of the other person's hand, the balls wouldn't flash and hum because it is a broken circuit.

10. Does it matter who lets go?

If anyone let's go, the circuit is broken so the ball will not work. So it does not matter who lets go.

11. Can you create a circuit where only one ball lights up?

Yes, you can create a circuit where only one ball lights up by creating a parallel circuit. If a person lets go, the flow would still continue, leaving one ball to work.

12. What is the minimum number of people required to complete this?

This question was not worded clearly, so it was confusing. The minimum number of people required to accomplish this would be 1. Each finger (4 in total) touch each metal contact and this would create a parallel circuit.

                                    

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Series and Parallel Series

          

                There are two kinds of circuits: series and parallel. In a series circuit, loads (such as a light bulb) are placed in a single path, whereas in a parallel circuit, they are placed side by side. If any part of the series circuit is disconnected or not connected properly, the circuit will not work. If a path is broken, in a parallel series, the current will stop flowing through there and will flow through other paths. 

Blog 2: Newspaper Structure Challenge

Ready, set, go!!!

           On Wednesday, Mr. Chung gave us an exciting task to complete. The challenge was to construct the tallest structure with 5 sheets of newspaper and a limited amount of tape.


          Our group discussed what shape the base should be to ensure that the structure wouldn't topple to one side as well as how the following layers should be built up. We settled on creating a large triangular base, but we eventually ended up with a rectangular base because it was too hard. The following layers got smaller and smaller until it became a thin, rolled up sheet. At the very top of the structure, we taped a small piece of paper to increase the height. Our structure was unstable so we had to press in the newspaper at some points to alter the balance. About 20 minutes after, Mr. Chung told us to bring the structures to the front of the room to measure the heights. In the end, our group won by a centimetre!!!

  
          One of the best ways to create a strong, tall structure would be to have a triangular or rectangular pyramid as the base. Then, you would roll of the rest of the newspaper into cylinders and tape them vertically, one on top of another. Like our group, you could cut thin strips of paper in the beginning and add it on to the structure in the end.       

        

Blog 1: Notes on Current Electricity

1. Electrons in a static state have energy, but they are more effective when they transfer their energy.

2. Electric current is the flow of charge with a symbol I.

3. Current is the total amount of charge moving past a point in a conductor per time taken.
                     
                                                  Formula:        I   =  Q / T

4. An ammeter is a current-measuring device that must be wired so that all current flows through it.

5. In direct current, the current flows in a single direction from the power supply through the conductor to a load and back to the power supply. 

6. In alternating current, the electrons occasionally reverse the route of their flow.

7. A circuit is a path of current, which is needed for any electrical device to function properly.

A simple circuit with a load (light bulb), power source (battery).

8. Electric potential difference (V or Voltage) is the work done per unit charge as a charge is moved between two points in an electric field.

                            Formula:    V   =   E / Q   or   V   =  W / Q


9. A voltemeter is a device that can be used to measure potential difference.


10. An Ampere is a unit for current and the base unit is Coulombs(C) per second.