Wind Turbine

In class we had the project to create a wind turbine.  A wind turbine is a type of generator.  And a generator is a device that turns mechanical energy into electrical energy.  This is done by inducing a current in loops and coils of wires.  When a magnet is moved over a coil of wire the electromagnetic field is changed and a voltage and current are induced.  So what a wind turbine does is it uses the mechanical energy of the wind to spin any amount of magnets over coils of wire.  The faster that the magnets move over the coils and the more magnets and coils that there are, the greater the induced current will be.   So the biggest challenge in all of this project was to get our magnets spinning quickly and closely to the coils in order to generate the most electricity.

                                                                        Motor 
In class I created a motor by using only a battery, a wire, a magnet, and some paper clips and rubber bands.  A motor is something that turns electrical energy into mechanical energy.  This is done when a current carrying wire experiences a change in its magnetic field, this is what the magnet is for.  When the magnetic field changes a torque is created.  This torque causes a rotation and it is that rotation that is used to do things.

                                          The Top Ten Times You See Physics In Football

"Down! Set...........  Hut!" The center snaps the ball and he and the other linemen take steps back to set up in cup pass protection. The center has great confidence that he will be able to block the blitzing linebacker that is shooting A gap.  This is because the center knows that he is much larger than the linebacker, and he also knows that an object at rest will stay at rest and an object in motion will stay in motion according to Newton;s first law.
 The QB now has the ball, he pushes off and begins to back peddle. But while he is doing so he thinks about how the only reason is is able to move is because he is pushing on the ground in one direction while the ground is pushing him back in the opposite direction.  This reminds him of Newton's third law which says that for every action there is an equal and opposite reaction.   Before he plants his feet and sets up to throw, the QB remembers how the vectors were used in his physics class to show the direction and forces during the cart and Buggy example.
                                                            
 The QB has set up, selected his target, and begins his throwing motion.  His arm extends up and out reaching nearly full extension.  He knows that if he wants to throw the ball far it will require a great force.  And one way to get a larger force is a greater velocity.  So by extending out his arm, the QB places the ball further from the axis of rotation (his shoulder).
By placing the ball further from the axis of rotation, it must have a greater tangential velocity in order to maintain the same rotational velocity.  What this results in is that the ball comes off of his hand with a high velocity and force that will propel the ball to its target.

As the QB releases the ball and watches it fly ever so gracefully through the air, he cannot help but to look up at the stadium lights and appreciate the physics that make night games possible.  He thinks back once more to that same physics class he had in high school where he learned about circuits and electricity.  He makes the assumption that the stadium lights are rigged up in a parallel circuit because some of the lights are on, while others are burnt out or turned off. He knows that a circuit must be complete in order for a current to flow, and is considering how a series circuit is inferior to a parallel because an entire series circuit will fail if there is any breakage at any point.  And at that moment his ribs experience some breakage as he is blindsided by the blitzing linebacker that the center was supposed to have picked up.
The ball is now flying through the air on its way towards the receiver.  (They say that the ball has a mind of its own, and this one happened to have a high school level understanding of physics concepts...)  As it is flying through the air it begins to realize that it is slowing down.   Thankfully the ball does not panic because it understands what is happening to it.  The ball is slowing down because it is experiencing air resistance.  And the ball knows that air resistance is determined by two factors, speed and surface area.  The ball can rest assured knowing that it has not gotten fatter, it has simply been going fast and so it was experiencing increased air resistance  causing it to slow down.
The receiver has just made his break on the ball and is preparing to catch the ball.   So naturally he thinks about how if he wants to decrease the force acting on the ball therefore catching it softer, he must increase the time it takes to come to a  stop in his hand.   The receiver understands that  p=mv  and he also understands that (delta)p=J and that to find (delta)p, you take p final- p initial.  Since J=F(delta)t  he increase the time that the ball is in contact with his hand in order to decrease the force.
The receiver has successfully caught the ball and turns his head to prepare to juke.  He sees that the safety is breaking down and is about to hit him.  The receiver then prepares for impact.  He bends his knees in order to lower his center of gravity and places his feet shoulder width apart in order to widen his base of support.  Because the receiver lowered his center of gravity and widened his base of support he was very difficult to push over and so was able to shrug of the tackle.
 There is now only one thing stopping the receiver from the end zone, a help side corner is running in really fast.  The receiver knows that he cant outrun the corner, but he knows how he can use his speed against him.  Right before the corner is about to lay a big hit on  him, the receiver stops in his tracks and the corner goes flying past him.  The receiver knows that this is because the corners inertia kept him moving in his current state and resisted change in motion such as the receivers sudden stop.
Touchdown!! Everyone goes crazy! Well except for the guy carrying his drink up the stairs in the top tier bleachers, he missed it cause he was busy doing work.  As he was walking up the stairs he was was doing work on his drink as he was moving with a force and a distance that was parallel.  
All the players are loading the bus after the win and get ready to drive back.   The punter who happened to be a physics minor in college thinks its pretty cool how the motor in the bus or any other motor is really nothing more than just a current carrying wire that is experiencing a force in its magnetic field causing a torque and making it rotate.

                                                                          UNIT 7

Hey wanna know something that's really attractive?......  MAGNETS!!!!!    

Yup, were gonna talk about magnets today.  

A magnet is an object that has its domains aligned in the same direction.   Well what are domains? 

Great question, domains are caused when the electrons in a certain area spin in the same direction.                                                                                                                                                                          

                     Aligned Domains = magnetized          Unaligned Domains = Not magnetized 

                       

Because a magnet has its domains all in the same direction, a magnetic field with a specific direction is present in and around a magnet.   Inside the magnet the field flows from south to north.
 But outside the magnet the field begins to turn around and flow from north to south.
The symbol used for magnetic field is 'b'. 

                                

The Earth also has a magnetic field just like a magnet.  Except the only confusing this about this is that the earths geographic north, is the magnetic south.  That is just silly in my opinion, and i think that whoever named the geographic north and south owes us an apology.   

The magnetic fields on Earth are responsible for some of the most amazing natural phenomena called the Northern lights. The Earth is constantly being bombarded by cosmic rays.  And most of the time theses rays are deflected back into space my the Ezarths magnetic field because they are moving perpendicular to the field.  However, at the poles some of the rays are not deflected by the magnetic field and make it into the atmosphere.   This results in a beautiful light show.  

               Electromagnetic induction: Ok,  what is that?      Glad you asked.
Electromagnetic induction is when the magnetic field of a non current carrying wire is disrupted.   What this causes is a change in voltage and potential energy which induces a current.  
This is a principle that we see everywhere.  At stoplights, credit card machines and metal detectors to name a few.

                        

All of this is based off of Michael Faradays's Law which tells us that when a magnetic field changes a voltage is caused.  And this discovery is the reason why teenagers are able to bankrupt their parents with the swipe of a card.


                                                       Motors  vs. Generators
Motors and generators are very similar in that they both use magnets and coils of wire.  Where they differ is what they produce.

A motor takes electric energy and turns it into mechanical energy by using a current carrying wire to feel a force and generate a torque.   This torque can be used to turn anything form the wheels or an RC car, to a hand mixer.

A generator turns mechanical energy into electric energy by having magnets spin over coils of wire (or vice-versa).  This is able to generate electric energy because when a magnet passes by a coil it induces a current.   This is the basic principle that we get our daily electricity from.  


            But what do you do when there is either to much or to little voltage flowing to your device?
WOW,  you are just full of great questions today.    Well the answer to that question is something called transformers.   Transformers at its most basic level are two different stacks of coils with varying numbers of loops depending on whether it is a step up, or step down transformer.
 
                    
This one above is a step up transformer because there are more loops in the secondary coil than in the first.  This means that the secondary will have a higher voltage.  
But wait, how can they have a current of voltage or any of that stuff if they are not touching?
Wow I should give you a medal because you ask just the most relevant questions.  :)
Well the answer to your question my friend is induction.  By using AC current the primary wire induces a current in the secondary wire without even needing to touch it.  Cool huh?

                                                                             Unit 6

This unit is all about charges and electricity.  First lets talk about the most basic aspect of electricity, Charges.  

Charges:  Come in two types.  Negative - and positive +.  If something has more negative charges then that object is itself considered to be a negatively charged.  Likewise if an object has more positive charges it will be positively charged.  However, when there is a balance of + and - charges the object is considered neutral.   

One more curious aspect of charges is that like charges repel each other   -    -         +      +

and that opposite charges attract each other   -+     

       There are three ways that an object can obtain a charge.

1) Direct contact. This occurs when two objects have a point of contact and electrons are transferred.

2) Friction.  This occurs when two objects rub against each other and one object will steel electrons from the other.

3) Induction.  this occurs when objects do not touch, but the force is great enough that the charges move into the other object. 

     Another important charge related thing is polarization.                    Polarization is what occurs when the charges in an object move to opposite sides of an object.  What this results in is the object becomes charged because there is an imbalance between the -  and + charges  in the object.  

Coulomb's law:  F=kq1q2/d^2

Hey wanna hear something shocking?  ELECTRICITY!!!! 

But really electricity is pretty cool.  The way that we measure electricity is in Amps  A.
Electricity flows in circuits like the ones that we used in class to light the light bulbs. 

In the picture above the light bulb lights up because it is connected to a completed and unbroken circuit.  This allows electricity to flow to the bulb.  But hold up. Why does electricity flow?   

Well this all has to do with voltage.  When there is a difference in potential energy, a voltage is induced.  this results in the flow of electricity called current.   

                                     Voltage = V 

                                     Current = I 

Ok, so back to the circuits.  Circuits themselves come in two types, series and parallel.  

Series circuits have one path for current to flow.  This means that when one portion of the circuit is broken, the whole thing fails.  

   

Parallel circuits have multiple paths for the current o flow.  This is helpful because it means that when one part fails, the rest of it can keep going.   

In things such as buildings, where electricity needs to go to multiple places, parallel circuits are very useful in that they allow certain things to have no current, and others to have current. All while keeping a complete circuit. 

The wires that make up circuits have differences in thicknesses and lengths.  And what this causes is varying resistance, 

 

                                               Increased length/thickness = increased resistance. 

Resistance = R

 

                                        The formula for current: I =V/R

                                                                     Mouse Trap Car Challenge

                 This project was called the mouse trap car challenge for a reason.  the entire thing proved to be much more difficult than we had all expected.  Even when my partner Rashad and I were able to complete the requirement of covering 5 meters, we found it incredibly difficult to improve upon our time of 5.51 seconds.  By using the formula v=d/t we found that the car traveled at a speed of 0.907 m/s.   All the factors that determined whether or not the car succeed or failed could be explained by physics concepts we had studied.


         
 

          Newtons first law states that an object in motion will stay in motion, and an object at rest will stay at rest unless acted upon by an outside force.  It was crucial that we understood this concept if the car was to succeed.  In order to take our non moving car at rest, to an object in motion, we would need to apply an external force.  In our case the force we used was created by our lever arm.  However, once we got the car rolling we faced another challenge that was much more difficult to over come. Friction.  Friction was the enemy say for two places on the car, the contact that our powered wheels had with the ground, and the contact of the string to the axle,  In every other place friction was not wanted.  We did not want friction because that would mean that there was an external force acting on our car and that meant that it could not continue in its motion.

         Newtons second law says that acceleration equals force over mass  a =f/m.  and in this example, acceleration is very important because we are trying to move the car a certain distance in as little time as possible.  Because we had the one mouse trap that was providing our force, the thing that we could change was the mass of our car.  If the mass was to great, then the car would have trouble accelerating. this was the problem we originally ran into. our car was to larger and we were unable to accelerate it quick enough.

        Newtons Third law states that for every action there is an equal and opposite reaction.
For this project we had the action and reaction pair of the car pushing the ground and the ground pushing the car.   This is how the car was able to move in a direction.   When the car exerted a force on the the axle and wheels, the wheels began to push against the ground.   The ground then pushed back on the wheels with a force that was both equal and opposite.  This caused the car to accelerate in the desired direction.

            Many factors played roles in whether or not the car was successful.  Such as the friction between the wheels and the ground and the fiction between the axle and the car.  In the case of the wheels and the ground, our original plan did not work well because we had very smooth wheels that did not generate enough friction.  we changed this by adding rubber tape to the new wheels. this increased the friction and helped our car accelerate better.
The other area where we had a friction problem was with our axle and the car.  However in this case we had to much friction.  This caused the wheels to not be able to spin freely and this reduced our speed and coasting ability.  while we were able to reduce the friction in our front axle, we were not able to reduce it in our back nearly as much.

             Another area of difficulty for us was the lever arm.  We originally thought that having a longer lever arm would be beneficial for us.  We were mistaken as the shorter lever arm pulled the same amount of string in a shorter amount of time and was therefore a better tool for powering our car.

Looking back on the project now, I wish that we had had a more solid plan that we could have implemented.  We more or less winged it. I also wish that we had started smaller and with a more basic plan, and then expanded. What we did was nearly opposite to that.  With all that said, this was actually a very fun project.   I enjoyed being able to build and tinker all while applying the physics concepts and knowledge.

And to our car,  Thank you,   you may not have been the best looking, nor the fastest, but by golly, you got the job done.   And for that, I thank you.

                                                                   Unit 5 Summary 

Work:

We started this unit of by talking about a thing called work. Well what is work you ask?  Good
question, thank you for asking.  Work is a transfer of energy and is responsible for generating power.   Work is the result of Force multiplied by distance.
                                                                                                 work = F x d 
The resulting work is measured in what are called Joules.  An example of this would be:
               If a man weighs 900 Newtons, and he goes up stairs that are 7 meters high, how much work was done?
            This is easy, we just plug in our force (900N)  x  Our distance (7m) =  6300J of work.
There is on final catch however.  the forces in work must be parallel or they will NOT generate work.

Power:  

Now that we understand work we can talk about power.  Power is determined by how quickly work is done.             The formula for this is
                                                             Power = work/time 
And power is measured in what are called watts.    no Not all pro defensive end for the Texans             JJ Watt    
Although he does generate a lot of power.

As an example, lets use our first question with work, and find how much power was generated.

 SO we know that we had done 6300J of work, and lets say that it had taken the man 10 seconds to climb the stairs.
Lets set up the equation:
   Power = 6300/10  =  630 watts

Congratulations you now can move from work all the way to power!  but we are not done yet.


Kinetic Energy: 

Energy is an objects ability to do work.  And kinetic energy is an energy that requires movement and is found by the equation below.
                                                    KE= 0.5(m)(v)^2 
So here is the funny thing about physics, its all connected.  So that work that we learned about earlier, yeah its coming back again.  Thats because another way to find work is by the change in kinetic energy.
what this looks like is                          Work = DeltaKE   (delta = change in)
And how is it that we find the change in KE?  By the formula below, that's how.
                                                                 Delta KE = KE final - KE initial 

So lets do an example shall we?

A 10 kg mouse is running at 5 meter per second.  How much kinetic energy does the mouse have?

Well first lets set up our equation.   KE= 0.5(m)(v)^2  and now lets fill it in with the information that we have.                                           KE= 0.5 (10)(5)^2
That leave us with                            KE= 125J                  And KE is measured in Joules as well.



Potential Energy:

Potential energy is a tricky one. This is because it is not actually energy.  Instead, potential energy is exactly what it sounds like, the potential that an object has to have energy.
That's kinda confusing, I understand.  So lets break it down shall we?

Potential Energy = mass x gravity x height.   So the potential energy of an object depends on three (but really just two) things.   The objects mass and the objects height.  Gravity is also important but because earths gravity is the same on everything it is not a variable to potential energy.  

Further more, the mass of an object does not simply change, and so the thing that determines an objects PE is its height.  As soon as the object leaves the ground it has a potential energy that increases as it gets higher from the ground.

And although height is an important factor in PE.  It is important to understand that movement is not required for potential energy.



Machines: 

Machines are fairly simple, especially the simple machines. "ba dum tisssssss"  bad jokes aside, there really is not to much to a machine.  At the end of the day, the machines job is to make the work you do easier.   But here is the catch, a machine does not make work less,  it only makes the force required in the work less.

We know that work = force x distance.  And so to decrease the force we must increase the distance.  We know that work in must equal work out, so we can not do any less work, but we can change how we do the work.  
For example a ramp.   A ramp increases the distance that an object covers meaning that it took less force to accomplish the same amount of work.

Mass of Meter Stick Challenge 

The challenge was to find the mass of a meter stick only using a table, a 100g weight, and the meter stick itself. 

The first step was to get the meter stick to balance on the edge of the table while the 100g weight was on one end  This looked something like the image below. 

To balance the stick we had to create a clock-wise torque that was equal to the counter clock-wise torque. Because torque = force x lever arm    we had to find the force of the end of the stick with the weight.   

Because we know that weight = mass x gravity we plugged that in to get the equation

                                                         weight = 100 x 9.8  =  980

 And at this time the length of the lever arm was 30 cm on the left side, and was 20 cm on the right because it extended to the center of gravity on the meter stick.  
Now that we have this we can plug in our equation:
                                                          980 x 30 = X  x  20
After solving this equation we discover that the meter stick has a mass of 1470 and we then convert this into grams by simply moving the decimal point to the left. this leaves us with 147 grams.

Unit Summary #4

We started this unit with the concept of Rotational Inertia.  Before we explain what Rotational Inertia is lets have a refresher of what inertia alone is.  

                            Inertia = the property of an object to resist changes in motion 

Now that we have been reminded of what inertia is, lets look at Rotational inertia.

                        Rotational Inertia = the property of an object to resist changes in spin

One factor that has a great impact on rotational inertia is the location of mass.   For example: 

                                

When the mass is placed closer to the axis of rotation it is easier to rotate

Conservation Of Angular Momentum

Conservation of angular momentum (otherwise known and rotational momentum) states that the angular momentum before is equal to the angular momentum after.    But what is angular momentum?

                           Angular momentum = rotational inertia x rotational velocity


Here is a video that my group made explaining this concept.
  

         

Tangential and Rotational Velocity

Have you ever wondered how trains stay on the tracks when they take a curve?  No, you haven't?  Well to bad, you're going to learn about it anyways. There are two major factors that keep the train on the tracks: Rotational Velocity, and Tangential Velocity. 

Rotational Velocity = how fast something rotates around its axis of rotation.

Tangential Velocity = How fast something would be moving it were traveling in a straight path. 

     

Take a look at this photo.  Do you see how the wheels are connected by the axle and do not rotate independently.  Also notice how the wheels are shaped.  How they taper, being wider on the inside and smaller on the outside.

Because the wheels are connected by an axle, they have the same rotational velocity. however, different parts of the wheels have different tangential velocities.

The parts of the wheel that are wider have so spin faster (thus having a greater rotational velocity) in order to keep of with the skinny parts of the wheels who do not have to go as fast to have the same rotational velocity.  

 So when the train comes into a curve, one side has its wheels touching the tracks with only its slower spinning narrow portion. And the other has its wider and faster spinning parts of the wheels touching the track.   What this causes is the wheels that are on the side of the train  spin faster, and push the train back into the center of the tracks.

Torque

Torque is a force that causes an object to rotate.    In case you did not know, when you fall over you are actually rotating and this is all about torque.   But what is torque?

                                                                                                  Torque = Force x Lever Arm 

What this equation tells us is that you can achieve a large torque either by a large force, or by a large lever arm. 

When you are trying to rotate a difficult bolt with a wrench.  You are already applying as much force as you can so what can you do to generate more torque?  If you said lengthen the lever arm then you are correct.  Because we know that torque = force x lever arm we can increase the torque on the bolt by adding a pipe to the end of the wrench, or by getting a longer wrench.

Another thing torque is responsible for is balance.
Balance is achieved  when the counter-clockwise torque = the clockwise torque.
                                     
Because torque can be hanged by either force or lever arm, the forces nor lever arms have to be equal in order to balance. All that is required is that their product on each side of the axis of rotation are equal to each other.

Center of Mass

Center of mass = average position of all an objects mass.  Also called the center of gravity, the center of mass is very important when it comes to things falling over or not falling over. For something to fall over, it must have its center of mass outside of its base of support. 

When a person is standing as this man in the picture is, they do not have a very wide base of support meaning that they would not have to rotate very far in order to place their center of gravity outside of their base of support.  

A famous example of this is the leaning tower of Pisa.
.          
As we can see. The tower is leaning a great amount, however it is not falling over because it still has its center of mass inside of its base of support.

Right here is a rime example of Torque.  this is some good science stuff right here!


I'm just kidding here is the real torque video, enjoy.

I  think this video is useful because it shows an important distinction between force and torque. Torque is what it takes to rotate an object.





 There is only one center of gravity in each object.  Before we know the actual location of the center of gravity we know for certain that it is within the base of support. The center of gravity does not even have to be actually touching the object it can be in empty space.