Energy!

What is energy? Energy is the capacity to do work. There are many different types of energy, the simplest one being mechanical kinetic energy, which is just movement. There is also things like light energy, thermal energy, chemical energy, sound energy, nuclear energy, and elastic energy.

Cannons!

BOOM!

We made cannons in class. (:

In order to maximize the range of the cannon, the angle needs to be 45.
We learned while doing projectile motion that the range of the projectile v2sin2(angle)/g.

Since sin90 is 1, and we want everything maximized, in order to get 1, the angle needs to be 45 because sin2(45) = sin90. (:



Even though that isn't a cannon, it is a projectile. (:

Newton's Problems

Over the past week or two, we learned about four of types of Newton's problems: Equilibrium, Inclines, Pulleys, and Trains. Now, at first, you might be like cause it can get confusing.
Don't worry, though! All you have to do is:
For all the problems, it is important to remember to break down all the vectors into x and y components.
There are also some tricks that can be used:
For equilibrium, remember that the acceleration is always zero, because the object isn't moving. That was pretty obvious.
For inclines, be lazy and tilt your head so you only have to break down one vector instead of two.
For pulleys, remember to draw two free body diagrams and treat the pulley as two systems, not one. Also, the acceleration of the whole system is the same.
Finally, for trains, also break it down into multiple FBDs. Acceleration is consistent, so when trying to figure it out, you only need to draw one FBD and figure it out from there. (:

See? Wasn't that easy? Now you can solve any simple Newton's Problem.

Projectile Motion

"A projectile is any object propelled through space by the exertion of a force which ceases after launch." (taken from wikipedia)

This is a projectile. In order to solve a projectile problem, there are certain things that need to be done. First off, the motion needs to be separated into two parts, x and y. The only thing common between the two is time.
For the x part, assuming there is no air resistance, the velocity is constant, and therefore there is no acceleration.
For the y part, because it is traveling vertically, there is gravitational pull. That means that acceleration due to gravity is always 9.8m/s^2 unless specified otherwise. We also know that whenever dropping an object, v1 is always 0.
By using these givens, it is possible to find any value in y by using the big five. In x, it is possible to solve without the big five.

Roller Coasters!

Time for my favourite roller coaster! I've never actually been on this one, but it's called Nagini's Revenge and it's at the Harry Potter Amusement park. And because I'm a total nerd, I have decided to blog about this one. (: This is the only picture I was able to find of it, which is a bit of a shame, but that's okay.

Looks pretty scary. :P

Adding Vectors

Firstly: What is a vector?
A vector is a quantity that is specified in both direction and magnitude. Vectors possess both a head and a tail, the tail being the start of the arrow and the head being the end of the arrow. Vectors are also written with direction, which can be indicated with and angle, or just a simple [N], [E], [S] or [W] for the simpler vectors.

The notation for the vector on the left would be 20m [N30W].

In order to add vectors, you must look at both the magnitude and the direction. The picture on the left shows how to add vectors that are going in the same or opposite directions. In order to add vectors that are not going in the same or opposite directions, we must use the Pythagorean Theorem. For example, if you have two arrows, one of them being 11km [N] and the other one being 11km [E], the resultant (R) can be found by using the formula a^2 + b^2 = c^2.

But wait, we're not done yet. Vectors have to have both magnitude and direction. We've already figured out magnitude, but now we have to figure out direction. This is explained by the next two pictures:

The Big Five

Andrea has kindly allowed me to steal this picture from her blog. (:

Equation number 3 is d = v1t + 1/2at2.
This can be derived from the graph. The first part of the equation is basically the area of the rectangle. The second part of the equation is basically the area of the triangle. Add them together and you get the area of the trapezoid. (:

Equation number 4 is d = v2t - 1/2at2
The first part of this equation is a big rectangle (b x h). The second part is the area of the triangle that isn't part of the graph. Subtract them and you get the area of the graph. (:

translating graphs

Original graphs (B)

(C)

(D)

(E)

(F)

(G)

And the graphs translated:

Motors (:

So in class today we made motors. That was pretty cool. We used things like wood, nails, corks, and a part of a pop can and it spun...or it was supposed to, anyway.

Ours worked on the second day, after making some slight changes.

We basically hammered nails into a wood base and tacked the brush onto the base as well. We stuck a kabob stick into a cork and stuck nails in it. Then we wrapped wire around it and hooked the whole thing up.

When the magnets were added (that's what the nails were for) and it was connected to the power source, it spun. (:

And there were sparks.


I thought this was relevant.

Right Hand Rules 1 and 2

Point your right thumb in the direction of the conventional current to use the rule

RHR 1. Basically when a conductor is conducting electricity, it creates a magnetic field around it. By applying the right-hand rule, you can figure out which way the magnetic lines are going.

 

The second RHR will help you figure out the direction of the north end of the temporary magnet when you have a conductor wrapped around a metal like iron. Your fingers represent the direction of the current (conventional current when using your right hand) and the direction your thumb is pointing is the direction the north pole of the magnet is. (:

10 points again

I'm sorry...I had to

• Magnetic force = force that acts at a distance
• magnetic field = distribution of magnetic force in a region
• north and south poles on a magnet
• north repels north, south repels south, north and south attract each other
• test compass is used to map a field
• earth is like a magnet
• magnets also attract metals that are not magnets (iron, nickel and cobalt)
• these are called ferromagnetic metals
• right- and left-hand rules
• ^ tbh I didn't quite get these rules

Moar Ten Points (pg. 553 - 563)

• current flow is dependent on the voltage of the power supply and the 'nature of the pathway through the loads that are using electric potential energy'
• the measure of the opposition to flow is called resistance
•  R = V/I
  R is the resistance in ohms (Ω)
• the V/I ratio is constant for a resistor
  the ratio is called "Ohm's law"
• thinner wire has a larger resistance than thicker wire
• resistance of a conductor depends on its length (the longer the wire, the greater the resistivity), cross-sectional area (the thicker the wire, the less resistant), the material it is made of (some materials are better conductors than others), and its temperature (greater heat = greater molecular motion = more particle impediment)
• R1/R2 = L1/L2, R1/R2 = A2/A1, R1/R2 = ρ1/ρ2
  L = length, A = area, ρ = resistivity
• series circuits connect loads in a single path
• parallel circuits connect them parallel to each other
• Kirchhoff's current law: the total amount of current that flows through a junction point is the same as the amount of current that flows out of it
• Kirchhoff's voltage law: the total amount of potential decrease in a circuit loop is equal to the total amount of potential increase in that same loop

Energy Balls

On Friday we had an activity with energy balls, which are balls like light up when used correctly.


1) Can you make the energy ball work? What do you think makes the ball flash and hum?
Yes. Closing the circuit (by touching the two metal pieces) makes the ball light up.

2) Why do you have to touch both metal contacts to make the ball work?
Touching both metal contacts closes the circuit. If you only touch one, the electrons cannot move through the entire circuit, meaning it can't light up the light.

3) Will the ball light up if you connect the contacts with any material?
No, it wont. The material has to be a conductor or else it will not allow the electrons to flow through it.

4) Which materials will make the metal ball work?
Metal, mostly. Also, salt water and human flesh, of course. (:

5) This ball does not work on certain individuals--what could cause this to happen?
Probably the most likely reason is if they're severely dehydrated. If someone's skin is very dry, it would not allow the electrons to flow through very easily, thus not completing the circuit and not causing the ball to light up.

6) Can you make the energy ball work with all 5-6 individuals? Will it work with the entire class?
Yes. (: It will work with 5 people and with the entire class.

7) What kind of circuit can you form with one energy ball?
A simple circuit. There is the battery, and light, and a conductor.

8) Given 2 balls, can you create a circuit where both balls light up?
Yes you can by creating a series circuit.

9) What do you think will happen if one person lets go of the other person's hand and why?
Both balls will stop lighting up because the circuit has been opened.

10) Does it matter who lets go? Try it.
 No, it doesn't matter who lets go. Anyone who lets go will act as a open switch in a circuit and the ball(s) will not light up.

11) Can you create a circuit where only one ball lights up (both balls must me included in the circuit)?
Yes you can. This type of circuit is called a parallel circuit. (:

12) What is the minimum number of people required to complete this?
You can actually do it with one person, but the balls would have to be held somewhat awkwardly. It does work, though.
 

Newspaper Structures

Our group's structure. (:

Each group was given 5 sheets of newspaper and some masking tape to build the tallest structure possible. Ours came in second.

Physics of Tall Structures: By making the lower part of the building heavier, it is able to support the weight of the higher, lighter levels. Also skyscrapers are supported by an underground substructure. Then, the weight is supported by vertical steel columns. Finally, horizontal steel girders support the weight of each floor.

Our structure didn't spread out the weight very well, but it still was able to stay standing.

What makes a tall structure stable? Spreading the weight out, steel supports, making the base larger than the top, etc..

Our structure wasn't completely stable, but it didn't fall down unless it was blown on.

What is the centre of gravity? It is a point on an object where the weight is equally balanced in all directions.

10 (+) points

·         Electrons transfer energy

·         Electric current = electrons repelling other electrons while passing through a conductor

·         Energy source -> gives electrons energy -> conductors transport electrons -> energy is transferred -> electrons transported back to source

·         I = Q/t

·         I is the current in amperes (A), Q is the chare in coulombs (C), and t is the time in seconds.

·         Flow of charge is called an electric current.

·         Ammeter is a current measuring device

·         In a direct current, the current flows in a single direction
power supply -> through conductor -> load (e.g. light bulb) -> back to power supply

·         In an alternating current, elections periodically reverse direction of flow

·         Circuit = path or current from positive side to negative side of power source

·         Black wire = negative, red wire = positive

·         V = E/Q

·         V is electric potential difference, E is energy required to increase the electric potential of a charge, Q.

·         E=VIt

·         E  is energy in Joules, V is the potential difference is volts, I is the current in amperes, and t is the time in seconds

·         Voltmeter measures potential difference