Wind Turbine

Wind turbines rely on...
   Electromagnetic induction: electromagnetic induction happens when a magnet moves through coils of wire. This changes the magnetic field of the wire which induces voltage which makes current which results in electrical energy. We used this concept to create a generator.
   Newtons first law: objects in motion stay in motion unless acted on by an outside force. This concept was useful because the blades stayed at rest until turned by the wind and would keep going if there was minimal friction. Because of this we tried to make as little friction as possible.
   Newtons second law: a=f/m. The acceleration of the wings equals the force divided by the mass. The more wind, the faster the blades spun. The more mass the wings had, the slower the blades would spin. It was important to have light blades because of this.
 
The materials we used were...
   cut up water bottles for blades to catch the wind and spin.
   dowels to hold the blades onto the machine.
   a metal rod to connect to the blades and spin the generator.
   magnets to attach to the metal rod so they can spin and create electromagnetic induction.
   coils of wire so when the magnets spin they create electromagnetic induction by changing the magnetic field of the wires which induces voltage which induces current.
   cardboard to keep the generator together and to use as a base to hold up the turbine.

Blades held on with dowels.

Machine held up by cardboard base.

Metal dowel to connect to blades and magnet.

Cardboard box containing generator. 

Coils of wire to make electromagnetic induction. 

Generator.

Coils of wire

Magnet spins when metal dowel is spun by blades.  

Our turbine.

Results...

   we generated .008 volts and .005 amps but were not able to light a lightbulb because we did not make enough because our blades didn't spin fast enough because there was too much friction. 

   Overall, our design worked very well. Our blades caught wind, our base was sturdy, and we had a good generator design. Our main problem was having too much friction. If we had more time, we would make the box big enough so that the magnets didn't scrape the sides of the box. 

   Our group worked very well together and I think the best thing that we did was making a very thorough plan instead of jumping right into building. 

 

Top Ten Places You Can See Physics At The State Track Meet

Over the weekend I went to the state track meet and saw a whole lot of physics!...

1. We drove to the meet in a bus. The bus is powered by a motor. The motor is supplied voltage from a battery which supplies current. The magnet supplies a magnetic field that makes charges move. The wires spin as a result of this current. The motor functions because there is a current carrying wire that feels a force from the magnets magnetic field and a torque is caused.

2. At the meet when people crossed the finish line they kept running for a bit before they slowed down. This is because of Newtons First Law which states that objects in motion stay in motion unless acted on by an outside force. In this case the runners are moving very fast and their bodies want to continue to do so. Because of this, even though they have crossed the finish line they keep going foreword while creating a lot of friction on the track until they stop.

The girl on the left is still running. 

I have crossed the finish line but continue to move

Emma has finished and stopped moving.

3. At the meet, people compete to see who can run at the fastest speed. Speed is the measure of the distance an object, or in this case a runner, travels in a designated amount of time. For example, my 4x800 team travelled 3200 meters at a speed of 10 minutes and 44 seconds.

My 4x8 team.

4. We can also measure how fast someone ran by using velocity. However, we could only use that measurement on the straight parts of the track because velocity requires a specific direction. If someone asked, "what was the velocity of that runner in 800?" you would say, "well, they rounded a curve which is not traveling in one direction so we can't measure their velocity". But if someone asked, "what was the velocity of that runner in the 100?" you would say, "well, they traveled in one direction so lets use the equation, v=d/t to find out".

5. We could also measure acceleration at a track meet. Acceleration is how fast an object picks up speed. We can measure this using the equation velocity/time.

Holt is accelerating by slowing down.

Rylynn is about to accelerate.

6. At the meet there was also long jump which is an example of projectile motion. The athlete jumps of the ground, sails up and then comes back down to the ground, trying to cover the longest distance. Lets say the jumper wants to cover 18 feet and jumps at a 45 degree angle. We can use the formula v=d/t to find the horizontal velocity. We can use the formula d=1/2gt^2 to find the vertical velocity. In order to find how fast the person was moving at any given time we use the pythagorean theorem.

Hank is in projectile motion.

7. In pole vault, once the athlete clears the bar, they fall down. This fall down is an example of free fall which is when an object falls due only to the acceleration of gravity. We can find out how far they fall/how high they jumped using the formula d=1/2gt^2. We can also find out how fast the person fell we can use the equation v=gt.

Elliott is about to free fall.

8. We can use Newtons Third Law and action and reaction pairs to understand how someone runs. Whatever force the person pushes back on the earth, the earth will push foreword that equal force. The person who pushes back harder on the earth will move faster.

Runners push ground, ground pushes runners.

9. Durring the track season I got a leg injury because I often ran on the hard track as opposed to the softer dirt trails. As we know from Newtons Third Law my foot goes from moving to not moving regardless of what surface my foot hits. Therefore my foot will have the same change in momentum regardless of the surface. Although my foot will have the same change in momentum, it will have a small amount of time to go from moving to not moving and therefore a large force on the track. On the trails, my foot will have a longer time to stop moving and therefore a small force so I will have less injury on the trails.










10. At the meet we ate sandwiches. The coaches used a credit card to buy those sandwiches. Credit cards work because of electromagnetic induction. In the credit card machine there is coils of wire. When the magnetic strip on the card goes through the colds, the magnetic field in the coil is changed. This induces a velocity which causes a current. This current sends a signal to the computer and allows the card to pay.

Go Blues!

Magnetism Unit Summary

Electromagnetic induction is when a change in the magnetic field of a wire loop induces voltage which causes current. This can be seen in traffic lights, airport metal detectors, credit card machines, and transformers. The magnetic field changes when a magnet moves through a coil of wire or vice versa.
In traffic lights for example, the metal of the car moves over coils of wire in the road which changes the wires magnetic field. This induces voltage which causes current. The current sends a signal to the light for it to turn green when there is a car there.
Transformers have no magnet but are made up of two current carrying wires next to each other. They are used to increase or decrease voltage and can be seen in most appliances such as refrigerators, hair dryers, computer chargers, washing machines, etc. The magnetic field of the primary wire changes because of its alternating current which causes a change in the magnetic field of the secondary which induces voltage which causes current.
Generators convert the mechanical energy of a spin into electric energy which is a change in current. Generators can be found in things like wind turbines or hydroelectric dams. In the case of the wind turbine, the wind spins the blades, the blades move the magnets through the wire or vice versa which changes the wires magnetic field which induces voltage which causes current.

Forces on Charged Particles are important when it comes to cosmic rays and motors. When cosmic rays, or charged particles approach the earth at its equator, the charges are moving perpendicularly to the earths magnetic field lines so they feel a force and do not enter. However if the particles approach the earth towards the geographic north, the charges are moving parallel with the earths magnetic field lines so they do not feel a force and they enter. This is what causes the northern lights and why the northern lights are only seen at the north and south of the earth. The geographic north and south are opposite from the magnetic north and south because of these magnetic field lines.
Motors are made of coils of wire and magnets and are the opposites of generators. They convert electrical energy from a battery or other power source to mechanical energy like the spinning of a wire. The current carrying wire feels a force in the magnetic field because of the magnet and this causes the torque of the wire.

Magnetic Fields are essential in understanding magnets and magnetism. The source of magnetism is moving charges. When charges move in a wire there is current. When something is magnetized, the domains of the object all line up with the magnetic field lines which go from south to north. Like poles repeal and opposites attract because the magnetic field lines need to be parallel in order for the poles to attract. An object can be magnetized if it is brought into contact with a magnetic field causing the domains to line up. Compasses are simply magnets that are free to move to line up with the earths magnetic field.  

Motors

In a motor, the battery supplies voltage which supplies current. The paperclips allow rotation and current to be conducted. The magnet supplies a magnetic field that makes charges move. The copper wire loop spins as a result of the flowing current. When creating my motor I scraped the wire only on the top of each side. This is because of the right hand rule so when current is perpendicular to the magnetic field a torque is caused.
In order for the motor to turn, there must be a current carrying wire that feels a force from the magnetic field of the magnet. This force causes a torque. The copper loop spins because it has moving charges in it from the magnetic field and the perpendicular current. The magnetic field goes upwards, the current goes to the right, and the wire turns because of this force/torque.
This motor can be used for many things, when something is attached to the ends of the wire. It could be used to power wheels, a fan, a mixer etc.

Charges and Polarization including Coulomb's law
Objects are charged when there are more protons or more electrons making objects positive or negative. This can happen because of friction, contact, or induction . Contact happens when something charged touches another object and transfers energy. Friction is when objects rub together and one steals electrons from the other. Induction charges an object without contact The reason that hair stands on end when a winter hat is taken off is because of friction. The hat becomes negative and the hair becomes positive and because opposites attract, the hair sticks up to try to get to the negative hat.  
Polarization is when the charges in a neutral object are separated. Polarization is how plastic wrap sticks to a bowl. Plastic wrap becomes negatively charged through friction when it is unwrapped. When it comes in contact with a bowl, the positive charges in the bowl move close to the negative wrap and the negative charges move away from the wrap. The distance between the attractive charges is smaller than that between the repelling charges (Coulums law: F=k q1 q2/d^2).
Electric Fields
  Electric fields are the area around a charge that can influence (push/pull) another charge. They are represented by arrows. The closer together they are the stronger the electric field is. The arrows show how a positive charge reacts. When two like charges are pushed closer together a stronger repulsion is created. Electronics are usually encased in metal because the metal creates a protective electric shield. The charges in electronics are sensitive and can not come in contact with others, so if a negative charge was encased by positive ones, it would feel no force no matter the location. Electric fields and shielding are also the reason that people in a car on power lines are safe.
Electric Potential/Electric Potential difference
The electric potential is the amount of energy stored up in an object. It equals electric potential energy/charge and is measured in volts. The electric potential difference is the difference between voltage. One power line has a different voltage than the other so when they are connected by something such as a birds wings, the circuit is complete and there is a difference in the electric potential. There is also a difference in electric potential when a car battery is jump started.
Ohm’s law and Resistance
Ohms law is I=v/r meaning that current is directly proportional to voltage and inversely proportional to resistance. Resistance is how easy or difficult it is for the electrons and energy to travel. Length, temperature, and width are factors of resistance. Resistance is measured in ohms.
Types of Current, source of electrons, Power
Current happens when there is electric potential difference. There are two different ways that electrons and energy move through a wire, alternating current (AC) and direct current (DC).
DC is when the electrons move foreword. AC is when electrons move back and forth. AC is the most commonly used current. When these electrons move, the power company is supplying the signal for them to move, not supplying the electrons which are already in the wire. Power is equal to current and voltage. It is measured in watts and is associated with brightness.
Parallel and Series Circuits
Energy and current is used in two different circuits, parallel and series. Series is like adding stop lights to a road while parallel is like adding lanes. Parallel is almost always the type of wiring used. In series as more bulbs are added, they get dimmer because the current decreases and the resistance increases. In parallel as more bulbs are added, they all stay the same brightness as before making current increase and resistance decrease. In order to make sure that there isn't too much voltage because of too much current and resistance, fuses are used. Fuses break and shut down the system to keep us safe.

Mousetrap Car

We were challenged to make a car powered by a mousetrap travel 5 meters. My car travelled 5 meters in 2.91 seconds and won first place.  Here is a video of it crossing the finish line:

 
As Newtons first law says, an object in motion stays in motion unless acted on by an outside force. In the case of our mousetrap car, once it got going from the power of the mousetrap, it kept going. Our challenge here, was to make sure that there was no opposing force such as running out of string or having too much friction.
As Newtons second law states, acceleration=force/mass. Because a big force or mass causes big acceleration, it was beneficial for us to have a relatively heavy car. However, it could not be so heavy that the mouse trap did not provide enough power to propel the car.
As Newtons third law states, every action will have an equal and opposite reaction. In the case of the mouse trap car, the car pushed the ground back and the ground pushed the car foreword. This action and reaction pair is what caused the acceleration of the car.

Friction was a very important factor in the mousetrap car that both benefited and hindered us. The force of friction from the ground caused the torque on the wheel. To increase this friction (but not make it too much friction so that the car doesn't move) we added rubber bands to our wheels. In order for the axles to spin, there must be little to no friction in that area. Because of this we made our axles out of colored pencils which are smooth, attached them with smooth metal eye hooks, and stabilized them with smooth electrical tape. We also needed friction between the string and the axle so that it moved so we attached the string with hot glue.

The mousetrap cars work well if they are large because the bigger the wheels, the bigger the lever arm (distance from axle to edge of wheel), the bigger the torque. However, the wheels couldn't be too big because they have more rotational inertia which will make the wheels more difficult to turn. Because of this we used CDs which are light, have a good sized lever arm, but still moved easily.
Lever arm also applied to the mousetrap.  Increasing the lever arm on the trap does not increase force but increases the amount of time that the force acts on the axle. Because of this increase in time and distance the force is decreased. We increased the lever arm to make the force act over a longer amount of time but we made it small enough so that there was still a large amount of force.

When the mousetrap is pulled back and set, potential energy is stored. It then gets converted into kinetic energy by being attached to the axle and making it spin.

Despite the power and energy, we can't calculate the amount of work the spring does on the car, the amount of potential and kinetic energy, or the force of the spring because the force and distance are not parallel.

                            rubber bands for friction, CDs for wheels, eye hooks to hold axles, Styrofoam for stability, colored pencil for axle, electrical tape so the axle stays straight, string for transferring power from mousetrap to axle, dowel for lever arm, mousetrap, wood body

Our first mousetrap car design was a tea box as a body with the mousetrap on top, colored pencil axles going through the body, mason jar top and CD wheels with rubber bands, and a string attached to the mousetrap, going through the body of the car and attached to the axle. This design failed because there was way to much friction on the axles and string, the axles were not parallel, the axles and wheels were not stable, the box was too light and flimsy, and the mason jar top wheels were bent and too small. In order to fix this, we added electrical tape to the places with too much friction, replaced the mason jar wheels with spools, old toy car wheels, and tape rolls and tried to adjust the axles to be straighter and more stable, added bolts and mason jar tops to make it heavier and we added wood to the box to make it more stable. The box, axles, and wheels were still to flimsy and there was still to much friction on the axles and string and between the wheels and box. We changed axles, wheels, and string countless times until we decided that the tea box would not work. We attached the mousetrap to a piece of wood and drilled eye hooks on either end. We put new colored pencils through these, attached CD wheels with rubber bands onto the axle with added support of Styrofoam (after trial and error with many other types of material) on either side to keep them straight. We added electrical tape between the eye hooks and the wheels so that the axle wouldn't move sideways but there was still very little friction. After that we made the string longer so that it wouldn't get stuck. The car was moving sideways because the wheels and axles were not completely straight so we added bolts and screws on the side to balance it out. That did not work so we took them off and changed the side that the lever arm was on. That still did not work so we reattached the wheels and their supports many times until they were very straight, messed around with the length on the string, and redid the eye hooks so that they were even. After 18 hours of work, our mousetrap car crossed the finish line.

If I were to do this project again I would make sure to measure everything very well as most of our problems came from adjustments because the axles or wheels weren't perfectly even. I would also make sure to have a very thought through and solid plan before starting as we jumped in to building too fast.
I would also make sure to continue to compromise, communicate and be flexible with both my partner and the car and continue to persevere no matter what.

Unit 5

   Work is force times distance (work=fxd). It can only occur when parallel, like a person picking up a cat up off the ground. If the person walked forward while holding the cat, work would not occur. Work is measured in joules.
   Power is work divided by time (power=work/time). Power is measured in watts and unlike work, which is required for power, requires time.
   Work is related to Kinetic energy because work= a change in kinetic energy. A change in kinetic energy = KEfinal-KEintitial. Kinetic energy = 1/2 m v ^2.
   There are three types of simple machines: ramps, levers, and pulleys. A simple machine decreases the amount of force needed by increasing the distance covered. For example, someone could pick a very heavy cat up off the ground, or they could push it up the ramp. Picking it straight up would require a large amount of force, but a short distance, but pushing it up the ramp would require much less force because it would be a longer distance.
   This happens because of conservation of energy. This means that the work in has to equal the work out. In the case of machines this trade of distance and force looks like this: fD=Fd. This concept can also be applied to a pendulum or a roller coaster. As far as a pendulum is pulled to one side, it will never get higher than that and a roller coasters hills can never be greater than the first one.
  This is because of potential and kinetic energy. Potential energy = mass x gravity x height. PE does not require motion, just height. When something is at the top of a fall, it has a certain amount of PE and no KE and at the very end of a fall it has no PE and a certain amount of KE.

Unit 4

Rotational speed is the number of rotations per amount of time. If a lady bug was sitting any where on an LP, it would always have a rotational speed of 33 1/3 rpm.
Tangential speed depends on the radial distance, or the distance from the axis of rotation.
Real life applications of these concepts can be seen in train wheels and gears. Gears work by moving at the same tangential velocity and different rotational velocity. Train wheels self correct by having the same rotational velocity but different tangential velocity.

Rotational inertia is how resistant something is to rotation and it involves the distance from the axis of rotation. If there is a meter stick with two weights taped very near the middle, it would rotate easier because it would have a short distance to the axis of rotation and therefore a lower rotational inertia. If there is a meter stick with two weights taped towards the end, it would be more difficult to rotate because it would have a long distance to the axis of rotation and therefore a higher rotational inertia.

Conservation of angular momentum  means that the torques are equal in a situation such as a figure skater extending their arms and then curling up. When a figure skater is extended, she moves much slower than she does when curled up. Despite this, the angular momentum is the same before and after because when extended, the skater has a small rotational velocity and a large rotational inertia and when curled up, the skater has a large rotational velocity and a small rotational inertia.

Torque causes rotation. Torque = force x lever arm (distance from the axis of rotation). A large force, a large force, or both, create a large torque. For instance, if someone was having a hard time using a wrench, they should get a longer wrench because it would increase the lever arm and therefore create more of a rotation. When something is balanced, its clockwise and counter clockwise torques are equal.

The center of gravity is the average location of mass in an object. The base of support is like the bottom of a box or someone's feet. When the center of gravity is above the base of support, there is no torque/rotation. Lovering the center of gravity makes it more difficult to rotate the center of gravity outside of the base of support. Making the base of support lower creates more stability as well.

Centripetal force is an inward seeking force. For instance the moon stays in orbit around the earth because of the centripetal force pulling it to earth and the fact that it wants to keep going straight.

Mass of a Meter Stick Challenge

Our goal was to find the mass of a meter stick using only a meter stick and a 100g weight.
In order to do this, we placed the weight on the very end of the meter stick and then balanced the meter stick on the edge of a table. When something is balanced, it means that its clockwise and counterclockwise torques are balanced. Because torque = force x lever arm, the force x lever arm of the right side equaled the force x lever arm of the left side.
On the left side we have the 100g weight. The force of this will be the mass of this weight multiplied by the force of gravity, 9.8. The force on the left is 980. The meter stick was balanced at the 30 centimeter point making the lever arm 30 cm.
On the right side, we do not know what the force is. The lever arm is from the point of balancing to the center of gravity of the entire stick which is at 50 cm. The lever arm of the right is 20cm long.
Our equation is 980 x 30 = x x 20. We solved using algebra to get...
1470. the decimal point must be moved over to convert it back into grams.
The mass is 1.47g.

Center of gravity + torque

Although the Leaning Tower of Pisa is leaning it does not fall down. This is because the tower's center of gravity is over, or within the base of support. Center of gravity is when gravity acts on a center of mass. The center of gravity is the average position of mass in an object.
In the picture below, the pink dot is the center of mass, the pink line is the center of gravity and the green is the base of support.  Although the object is leaning it is not falling over because its pink center of gravity is within the green base of support. In the second picture the pink center of gravity is not within the green base of support. Therefore the object will have a blue force resulting in an orange lever arm. A lever arm is the distance from the axis of rotation, or where the object rotates from. When something falls it rotates. In order for something to fall, torque is required because it causes rotation (torque=forcexleverarm). In order to have a large torque, the object must have either a large force or a large lever arm or both. The larger the torque, the larger the rotation. In the situation below, the object falls because its center of gravity (pink) is outside the base of support (green), has a lever arm (orange), and therefore has a torque which causes the object to fall.