Unit Blog Reflection

This unit we learned about electric currents and electric fields, including Ohm's law and Coulomb's law, which are I=V/R, and F= ke q1q2/r^2.  We also learned about electric fields, and what the diagrams portraying electric fields actually mean, which is that the arrows in the diagram  are the direction that a positively charged particle will go when placed into that electric field.  Besides that, we also learned about the different kinds of ways that an object can gain a static charge, which are through either friction, induction or .  Friction occurs when rubbing two objects together, induction occurs through polarizing an object and then drawing off the positive charges with another object, and .  After that we learned about electric currents, and that the electric charge in a current doesn't really flow through the wire (or whatever object is carrying the current), it needs to fill the entire thing at once, or else it can't flow at all.

This is an example of a simple electric circuit.  The battery is the source of the electric field, the switch exists to break the current and the lightbulb is the thing being powered by the current.

The different kinds of electrical circuits are called series circuits and parallel circuits.  Series circuits have everything on one wire, while parallel circuits have multiple wires independent of each other connected to the same source.  If one segment of line goes down in a series circuit, it shuts off the whole thing but for a parallel circuit any of them can be broken and not affect the others.

       This unit may be the one that effects our real lives the most, because everyone uses electricity.  It's good to understand how it actually works.  The things I had trouble with were mostly remembering the formula's, and in truth I still haven't quite got them down.  However, when I do it will mostly be through repetition.

Current Resource

This is a video from Khan Academy talking about circuits.  It is part of a series of 4 videos, but in this one he talks about current, resistance, and voltage.

Voltage Resource

This is a video of some maintenance workers playing with a power line.  In it, you can see how they are using heavily insulated suits, and still have electricity arcing from the power line to their hands.  You can hear the electricity moving through the air and it gives a very visual representation of an example of high amounts of current.

Mousetrap car

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Mine and Manuel's car traveled exactly five meters in just over nine seconds.  It involves Newton's First and Second laws, using the inertia of the mousetrap to keep it in place as it spins the axle, as Newton's first law states that an object at rest will stay at rest unless acted on by an outside force, and an object in motion will stay in motion unless acted on by an outside force.  We attached a 100 gram weight to the mousetrap to increase it's mass which also increases the force required to make it move.  When it can move the axle without being moved itself, the car moves.  We didn't increase the lever arm of the mousetrap, which may have contributed to it only going five meters.  Our mousetrap car moved very slowly, because it had a lot of mass, therefore the comparatively small force of the mousetrap closing was not enough to make it move quickly.  We used two frisbees, a pencil, a piece of wood and the mousetrap to make our car.  The mass may also have contributed to how quickly it stopped once the lever arm stopped moving it.

Reflection:  Our mousetrap car was very makeshift.  We are lucky it worked at all.   If we could do it again I would spend more time gathering materials, and also make sure that we had our mousetrap before the say of the final run.  Just in general, more effort all around would be nice.

Blog Reflection 2-17

Summary
Difficulties
overcoming the difficulties
relate it to real life


In this unit we learned about work and energy, and the relations in between the two.  Work is a function of how much force you put on an object, and the distance over which that force occurs, using the formula Work=Force x Distance.  Work is measured in Joules.  Power is related to work, in that work divided by the time (in seconds) that it takes place over will give you the power generated by that action.  For example, if you do 1000J of work over 5 seconds, that will be 200 watts of power.  Kinetic Energy is related to work, in that the work done on an object is equal to the change in kinetic energy of that object.  The formula for finding kinetic energy without knowing the work is KE=1/2 mv^2.  Potential Energy is sort of like Kinetic Energy's evil twin.  If an object has an amount of potential energy (found using the formula PE=weight x height), than as it releases that potential energy, it is transformed into kinetic energy.  Machines are devices used to decrease the amount of force it takes to do a certain amount of work by artificially increasing the distance.  However, you cannot get more work out of a machine than you put into it.

Some difficulty I had with this unit was remembering all of the different formulas.  I mostly managed to remember by simply going over them repeatedly, but I didn't quite manage to memorize the formula for potential energy.

This unit is one of the most connected to real life that we have had for a while.  It teaches us about the energy things have while they are in motion, as well as how machines function.

Work Resource

This is a video from Khan Academy about an introduction to work and energy, and how they relate to one another.  Khan Academy do very good tutorials, so this is a comprehensive lesson on the subject.

Unit Blog Reflection

Unit Blog Reflection

This unit I learned a lot about things that spin around, such as their angular momentum, which is the quotient of the rotational inertia and the rotational velocity.  Rotational inertia is the “laziness” of a rotating object, or it’s resistance to being spun faster or slower.  If something has a lower rotational inertia, but the same energy as something with equal mass, it will spin faster even if they both started with the same rotational velocity.  Rotational velocity, meanwhile, is how fast something is spinning, and is directly influenced by rotational inertia.  The angular momentum will be the same regardless of whether the object is spinning quickly with a low rotational inertia, or if the object is spinning slowly with a high rotational inertia.  I also learned about the different kinds of velocities when an abject is spinning.  Rotational velocity is one of them, but there is also tangential velocity, and they are very different.  For example, if two gears, one small and with 10 teeth, and the other one large and with 20 teeth, are interlocked and spinning together at a rate in which the larger one spins once per second, they will have the same tangential velocities, because they are both spinning at a rate of 20 teeth per second, even though that is two rotations for one of them and one rotation for the other.  However, because one of them has to spin twice as fast to have the same tangential velocity, it therefore has a higher rotational velocity.  We also learned about torque, specifically the effect torque has on your center of gravity and the amount of force you can apply to an object.