Top Ten Applications of Physics

10.  The number tenth application for physics is using it to find out the gravitational potential energy of an object, using the formula PE=mass times gravity times height.  You can use this to figure out how hard something will hit the ground when dropped from a certain height.
9. The number ninth application for physics in the real world is determining the kinetic energy of an object with the formula KE=1/2mv squared.  You can use this to figure out the force something is going to hit you with, or how much energy an object has while it is moving.
8. The eighth application for physics in real life is determining the rotational velocity of a wheel.
The rotational velocity is how many rotations per second a wheel goes, and this is used for things like figuring out how fast a car is moving.
7.  Number seven is using torque.  Torque is Force times a Lever arm, and it is used to leverage your strength to do things that you normally couldn't, such as turning a really stubborn bolt, or cutting through steel with a really big pair of scissors.
6.  Number six, Gravity.  The way to find out the gravatic attraction is between two objects is:
Gravity= g(m1 times m2)/d^2.  We use this to figure out how much attraction is between satellites and earth, and gravity itself binds the universe together.
5.  Number 5 is centripetal force.  Centripetal force is the thing that causes you to be forced up against the side of a car that is spinning in circles.  You use it every time you wash your clothes, because the spinning motion of the washing machine causes the water to force itself out of the turbine, letting your clothes get spun dry(er).
4.  Electricity!  Without electricity we would not have any of our wonderful technology that we use today.  Electricity is a current, and current is voltage/resistance, which is shown by Ohm's law.
3. Circuits are methods of moving electricity from one place to another.  They have to be a completed loop, and you can turn the flow of electricity on and off by breaking the circuit.
2. Magnetism.  Magnetism is a product of aligned domains in ferromagnetic materials.  Domains get aligned when either subjected to an aligned magnetic field, or getting hit with something while exposed to a very weak magnetic field (such as the Earth's field).
1.  Number one is generators.  Generators are ways of producing electricity by moving a magnet across coils of conductive wire.  You input force, and out comes electricity.  This is the best way to produce electricity.

Wind Turbine Blog

Me and Manuel constructed our wind turbine using several pieces of PVC pipe, and well as a plastic dustpan and the magnets and copper wire that were used to make the generator.  What we did was that we used the PVC pipe to make the housing of the wind turbine, and cut the dustpan into a pinwheel design, in order to catch the wind more effectively.  Inside the housing, we attached four coils of wire on the interior of the pipe, and to the turbine shaft we attacked four magnets.  As the turbine spun, the magnets would spin over the coils, generating electricity.

Blog Reflection 5-12

In this unit we studied electricity and magnetism, as well as practical applications of each.  We learned about the directions of magnetic fields, and about how the field flows from the north pole of the magnet to the south pole of the magnet, and about why the like poles repel each other, while opposite poles are attracted to each other.  We also built an electric motor, made out of a magnet, a battery, a coil of copper wire and a paperclip.  A motor is like the reverse of a generator, in that a motor takes electrical power and generates force, while a generator takes force and uses it to move a turbine to generate electrical power.  Certain electric cars can convert their motors to generators when they are coasting.  We also learned about transformers, and about how they only work with alternating current and not direct current.  The equation to find the change in voltage from primary to secondary, (input to output) is Vp/Tp = Vs/Ts where V is voltage and T is turns.  we also learned about how magnets generate a magnetic field due to the fact that they have aligned domains, which are groups of electrons and that any ferrous metal exposed to a magnetic field will start to generate an identical magnetic field of it's own.  This includes nails exposed to the earths magnetic field and hit with a hammer.
        I had no particular difficulties with this chapter, but once again, the formulas were troublesome.

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.  

Meter Stick Blog

     The meter stick, when it is balanced on the table, does not have a torque because each side of the meter stick has a torque, but in opposite directions (clockwise vs counterclockwise), so they cancel out.  The center of gravity of the meter stick changes when you add the 100 gram weight, in order to ensure that both sides (when balanced) have the same torque.
     To figure out how much the meter stick weighs, we (me and Manuel) measured where the new center of gravity was with the weight, and it was 24.4 cm from the edge of the meter stick.  The center of gravity for the meter stick was 50.6 cm.  We had to find the torque of one side of the meter stick, so we used the one with the weight on it, where we knew both the force downward (9.8 times .1) and the lever arm (.24).  Using those numbers, we got the torque as .239 N.  We then plugged that number into the other side, with the equation .239=(.506-.244)(Force), with Force being the weight of the meter stick.
     With this equation set up, all we had to do was solve it, then convert the answer from .912 Newtons, to grams, which gave us the answer of 92.85 grams.  The actual weight was 92.1 grams.
   

(Labelled drawing in progress)

Torque Resource

The video is from a series that contains tutorials on various different subjects, namely Khan Academy and this one is on the subject of torque.  It is really just a video that will teach you about torque through use of a sort of digital blackboard to illustrate the lessons that the narrator is giving.

Rotational Inertia resource

This video shows a spin from an ice skater that, when she tucks in her arms and legs, reaches up to over 300 rpm.  I thought this was a very good video to show off rotational inertia, as it is very clear that she is able to reach those speeds only after tucking in her arms and legs.