Top 10 Physics Blog

10: Tides
I had always wondered how the tides worked and why they changed the way they did, and now I know that it is because of the differences in gravitational forces caused by the moon and NOT the sun. Neap tides are when the moon and sun are at perpendicular sides of the earth, and these make for less severe highs and lows, while a Spring tide occurs when the sun and moon are in a line, this makes for higher highs and lower lows.

9: Stoplights
Many times I had been sitting at a stoplight in my car wondering how a stoplight knows that a car is there. With knowledge of electromagnetism, I can now see how the everyday stoplights work, and understand how genius the design is. When a car moves over coils of wire that are embedded in the ground, then the car amplifies the magnetic field of the earth, therefore inducing a voltage and a current in the wires. This current is read by a computer which tells the stoplight that a car is waiting.

8: Trajectory/ Thrown Objects
This lesson applies heavily to my life as a football player and the trajectory/ flight path of the football when thrown. Since all objects are acted upon by gravity, the flight path of a thrown object will be a parabola, the object will be at the same height twice in its flight path.

7: Momentum
This lesson was fun to learn because it let me know that mass isn't everything when it comes to momentum. For example a smaller football player can have more momentum than a larger player moving slower. Momentum = mass x velocity, therefore if a smaller object is moving really really fast then it will have a greater momentum than a slow moving large object.

6: Energy
The concept of transferring kinetic energy to potential energy was a fun one to learn. Kinetic Energy is the energy of motion, and can be found by KE= 1/2mv^2. Potential energy is equal to Mass x gravity x height or mgh. Energy can never be created or destroyed so one type of energy must transfer to the other. For example when an object is swung from a pendulum, it starts off not moving with only potential energy, but when it it starts moving some of its potential energy is transferred into kinetic energy.

5: Tangential vs Rotational motion
The difference between tangential and rotational motion can be seen in my life at track meets very frequently and is fun to think about. Tangential motion is the distance covered in a given amount of time by a rotating object, for example a gear might cover 12 prongs in 30 seconds. Rotational motion is the amount of rotations per given time, for example 3 rotations in 40 seconds.

4: Skydiving
Learning about skydiving was an interesting topic to learn and I had fun thinking about why air resistance works the way it does. When skydiving, your acceleration will only decrease from the point when you jump out of the plane or helicopter, but you keep speeding up until your air resistance equals your weight, this is called Terminal Velocity. Terminal Velocity is the fastest that an object can physically fall.

3: Rotational Inertia
Learning about rotational inertia was fun to learn about because you can see examples of it in life such as ice skating and rotating on a chair. Rotational Inertia is the tendency of an object to resist angular motion, the higher the rotational inertia, the harder it will be to start or stop rotating the object. Rotational inertia is based on an object's mass, and the distribution of said mass.

2: Conservation of Momentum
The conservation of momentum was fun to learn because I had always wondered why if you caught a ball on a frictionless surface then you would slide. Momentum will always be conserved in a system, and when you catch a ball, the momentum from the movement of the ball must be conserved and transferred into you.

1: Airbags
Learning how airbags keep us safe was really fun! Since Airbags increase the time over which your head or body is stopped, there will be less of a force on your body. This is because your body undergoes the same impulse to stop regardless of how you are stopped. Impulse = Force x time. Less force on your body means less chance for injury!

Windmill Blog Post

PVC pipe

1.) To know how a windmill design works, someone would need to know how Electromagnetic induction works. This is to say that when a magnetic field is changed near a wire then a current is induced in the wire, note that the magnetic field must be CHANGING. The coils of wire carry a current to whatever you may be powering, or to a generator. The magnets create a magnetic field that is moved near the wire to induce a current.

2.) to reproduce our design, one would need:
Plastic spoons
PVC Pipes
Coils of wire (copper preferably)
Magnets
Wooden Dowels
PVC Caps
Wooden Circles




Attach a pvc pipe to a pvc connector, drill hole in pvc cap. Connect pvc to more pvc and then to a base. Drill hole in center of wooden cirlce and insert wooden dowel. Glue plastic spoons in perpendicular directions every 90 degrees. Attach coils of wire to inside of pvc cap with ends of wire protruding from pvc pipe. Glue magnets in alternating North South pole arrangement on wooden dowel. inert wooden dowel into the pvc cap, and then it's ready to go! make sure the magnets are near the coils of wire so that maximum current can be achieved. When the fan blows on the spoons, the dowel will rotate as will the magnets which will change a magnetic field from North to South over the coil of wire which will induce a current.

3.) The factors that affect the induced current are the speed at which the magnetic fields are changed, the amount of wire that is present, and the proximity to the wire the magnets are. The 4 wire coil design worked very very well to produce lots of current. The closer to the wire that the magnets are, the more current that will be induced.
Video of our Windmill: http://www.facebook.com/l.php?
u=http%3A%2F%2Fyoutu.be%2FweLWy9qH7e4&h=tAQH0i_Lk

Magnetism Unit Review

Source of all Magnetism: Moving Charges
What is a Magnetic Field?
- Area of influence created by moving charges, particles have to be moving PERPENDICULAR to said field to feel a force
A magnetized object has Magnetic Poles, North and South
Domains are groups of electrons that spin in the same direction
an object can become a magnet itself if its domains become aligned, usually from another magnet.
When a fara-magnetic object comes into a magnetic field, it increases the strength of said magnetic field.
Electromagnetism is a word to describe a magnetic field caused by electricity
Motors are made of Coils of wire and Magnets. When a current is run through the coils of wire, the resulting force vector caused by the magnetic field produced by the magnet puts a torque on the coil of wire. Note that current has to be alternated for this to work. For example when we made motors.
Magnetic Induction:
When you start with electricity to produce a magnetic field, it is called Magnetic Induction. This is done by running a current through wires. When starting with a magnetic field to produce electricity it is called Electric Induction. Both are at play in Transformers. Transformers are two different coils of wire that aren't touching each other but are next to each other. When current is changed in one of them, a magnetic field is induced. This change in magnetic field causes a current to flow in the second coil of wire. Transformers can be used to step voltage up or down by changing the number of loops, otherwise known as turns, in the coil. Double the turns= double the voltage. Note that this only works with alternating current because it is a change in magnetic field that produces a current.

Generators have similar design to motors, only its role is reversed. A generator will store mechanical energy as electrical energy.

Credit Cards:
Credit cards have a magnetic strip that include specifically coded and uniquely magnetic sectors. The Card reader has Coils of wire within it. When the magnetic strip is run through the card reader, a specific amount of current is created by the magnetic field from the coded sectors. This current is then translated by a computer into the original code (numbers).

Primary Voltage/Number of turns = Secondary voltage/ number of turns

power is always conserved, power in = power out
Voltage x Current= Voltage x Current
VI in = VI out
For long distances it is better to have less current in a power line due to the excess loss of energy to heat from high current. This loss of energy means that the power companies are not getting as much profit. Note, however, that the Voltage increases while the Current decreases.

Paperclips- you can turn a paperclip into a magnet by putting it in a magnetic field to realign its domains to match the magnetic field. When the magnet is removed, the paper clip will produce its own magnetic field.

Magnetic objects stick together because when their poles are in the same direction, their force vectors and in the same direction. This means that they will add together and the net force will be attractive.

Motor Blog

Function of Each part of the Motor:
Battery: provided a current through the system
Paper clips: acted as both a conductor for the current and held the motor loop up
Motor loop: main rotary piece of the motor, carried current and spun
Magnet: Creates magnetic field that puts torque on the motor loop

We scraped the armature by scraping one side completely off so that there was no insulator, and the other side so that there was half of the wire without insulator. We did this because when the motor loop would turn half way, it would want to reverse directions, therefore we had to have the current be cut off so that the motor loop could keep rotating.

The motor turns because a current is running through the motor loop. When this occurs, the magnetic field from both the moving charges and the magnet placed on the system create a force that puts a torque on the loop. This works until it half way rotates and wants to reverse directions per the magnet. This is why we stripped the armature to have the current turn off when the motor loop would want to reverse directions. The direction of force needed to be perpendicular to the plane of the motor loop so that it would create a torque.

This motor could be used for educational purposes, as it does not do enough work to actually be useful in anything else.
http://www.youtube.com/watch?v=YQCZ-60fxXQ&feature=youtu.be

Electricity Unit Blog Reflection

Electricity

Charged: When an object is charged, it has either more electrons or less electrons than it has protons, and it will therefore exert a force on other charges in the world around it

Polarization: When a charged object approaches a neutral object (or another charged object), the charges within the second object separate as to have the opposite, attractive charges be closer together, and the like, repelling charges further away from each other.

Different ways to charge an object: 

Contact

Friction

Induction

Electric Fields:

An electric field is the area of influence that a charged object has on other objects around it

Vector arrows point in the direction that a positive charge would be forced

A negative charge will be forced in the opposite direction of these vector arrows

Farraday's Cage

A farraday's cage is something (usually a metal casing) that disperses charges equally around it so that any object inside will feel Zero Net Force on it. This can be seen in computers or other valuable electronics that are protected with a metal case. This is also called Electric Shielding

Voltage:

Voltage is the difference in electric potential between two points. the formula for voltage is V=Change in PE/q (charge)

Voltage in household appliances is fixed at a certain, unchanging value.

Coulomb's Law

Coulomb's law states that an object's force is equal to a constant, k, times charges one and two all over distance squared (F=kq1q2/d^2)

This is how we can explain a balloon sticking to a wall after being rubbed in one's hair, and also how we can explain part of how plastic wrap sticks to a plastic bowl.

Lightning:

Lightning works by first having negatively charged clouds that get close to the ground. This negative charge polarizes the neutral earth and brings the positive charges closest to the surface of the earth. When the attractive force between these opposite charges gets to be too much (along with a little added energy), a pathway is formed from the cloud to the earth, and the charges rush to the earth creating the flash that we all know.

We use lightning rods to have lightning strike the rods which are more conductive, then the charges travel down a direct path to the Earth, rather than going through the house and leaving little to no damage.

Circuits:

Circuits can be as simple as someone touching an electrified fence while standing on the ground, or they can be as complicated as the wiring within buildings. 

For charges to flow, a circuit must be complete with no gaps.

Types of Circuits:

Series: more appliances= same current but "dimmer appliances", one appliance stops working= whole circuit stops

Parallel: More appliances= more current, one appliance stops working= rest keep working

Current: the flow of charges in a circuit (amps)

Resistance: the factor in electrical circuits that inhibits current (ohms)

Ohm's law: V=IR (Voltage= current x resistance)

Power= Energy/ time, Voltage x Current

Fuses protect household appliances and the wiring of a certain area. This works by having the conductor that bridges the two sides of the fuse being rated for a certain current, when the current gets too high this conductor melts and therefore switches the circuit off. Fuses are wired in series so that when they melt, the whole circuit turns off. This protects wiring as when current rises too high the wires start to combust which is dangerous.

As heat rises, current decreases, resistance increases. This is what causes light bulbs to blow right as you turn your lights on.

My effort and Problem solving skills this unit

My effort in this class has been fairly consistent for this unit, asking questions when I struggled with a concept, and learning to the best of my ability. I did not encounter too many problems that I struggled with. This unit has answered a few questions that I always had when people discussed electricity and how it works in houses and other buildings. 

My goal is to keep strong effort and try my best to keep up strong grades to end the year.

Ohm's Law Resource

This video perfectly goes over what voltage, current, and resistance are and how they are all related. This provides a clear explanation for subjects that we have just covered so it proves as a great review resource or learning tool for anyone. I highly recommend this video for anyone who needs review or for anyone who wants to learn about Ohm's law.

Voltage Resource

This video offers a great explanation of what Voltage is and how it relates to both Charge and DIFFERENCE in potential energy. It provides the equation for Voltage as well as providing a few examples to make sure viewers understand the subject well. I would recommend this video for anyone who is looking to learn about voltage or anyone who is reviewing voltage. The only problem that I see with it is that the video is a little long, longer than 9 minutes.

Mousetrap Car Reflection

1. 2.91 seconds. 2nd in the class, _____ in the grade.
2.

3. 

4.

a. Newton's first law (an object in motion will stay in motion, an object at rest will stay at rest, unless acted upon by an outside force) applied to the moustrap cars because we had to figure out the right car design to allow the cars to continue in motion as per their tendencies. This means finding ways to have as little friction as possible in the design of the Car.

Newton's 2nd law (Acceleration is proportional to the net force over the mass of an object) was key in designing our cars as we had to find the best design to allow for a larger force and therefore a larger acceleration of the car. This meant having as little excess mass as possible and maximizing the force that was available from the mousetrap.

Newton's 3rd law (every action has an equal and opposite reaction) was key in the design of the wheels of the car. Without this law, the car would not go. The action/reaction pair in this circumstance is that the wheels push the ground back, ground pushes wheels forward.

b. The two types of friction present in the car were Rolling friction and Sliding friction. The rolling friction was present in the wheels rolling across the ground while the sliding friction was present whenever a moving piece of the car was rubbing against the static parts of the car. Friction in the moustrap cars was not good for the goals that we were presented with. We had to have as little friction as possible in order to have our car maintain a higher speed for a long amount of time and to allow the car to go the 5 meters. Our car's front wheels would slide against the eye hooks holding them in place, to fix this we replaced the front wheel with a 2 wheel design where the 2 wheels weren't near any other part of the car. We used friction to our advantage with the back wheels by wrapping balloons around them. This allowed for the car to get more grip on the ground via friction and therefore had an easier time accelerating.

c. To decide the number of wheels we had to take into account how the car's turning would be affected by the number of wheels present. We found that our 1 wheel design that we originally had would often turn towards a wall. This was when we replaced the 1 wheel with 2 wheels that offered more stability. We used smaller wheels in the front of the car and bigger wheels in the back axle. Having larger back wheels allowed for more tangential velocity while having the same rotational velocity, this means that more distance will be covered with each rotation of the axle. Having smaller front wheels allowed for both the stabilization of the car and also allowed for as little friction possible to be present.

d. The conservation of energy related to the car as to have the car go the requested 5 meters, the car's design had to conserve energy as it went, meaning that we had to have as little friction present as possible. The car also had a set amount of spring-potential energy stored in the spring of the mousetrap. This energy was transferred to kinetic energy when the mousetrap pulled on the string connected to the wheels of the car, therefore making the car move forward. 

e. Originally we had a large lever arm to try and disperse the force over a long distance, but after that design failed we removed the elongated lever arm and used only the distance of the mousetrap. This allowed for more pulling force as Torque= Force x Lever arm. With the same amount of torque and a shorter lever arm, there must be a bigger pulling force to compensate. The power output of the car was increased when the lever arm was shortened for our car as the time to cross the line was decreased, and since power= work/ time and the work was the same, a shorter time meant more power. 

f. Rotational inertia determined how hard it would be to start and stop moving the axles which were attached to the wheels of the car. Rotational velocity determined how fast the axles were rotating, this determined how fast the wheels would rotate. Tangential velocity was determined both by the size of the wheels and by the rotational velocity of the axles. Bigger wheels and high rotational velocity meant that the tangential velocity would be high. 

g. We cannot calculate the work that the spring did on the car because the spring pushed in a direction that wasn't parallel to the distance covered by the car all the way through the path of the spring. We cannot calculate the potential energy stored in the spring because each spring was different and we do not know the distance it was pulled back, we did not know its weight either. We do not know the velocity of the cars and we do not know mass of the cars. We cannot calculate the force the spring exerted on the car to accelerate it because this is the real world and some of that force and energy will be lost due to friction and noise and other variables. 

A. Our final design used a different, 2 wheel front wheel design, and a different, shorter, lever arm design. These changes were prompted by the fact that our car did not go the 5 meters and that it did not go very fast. 

B. The major problems encountered with our car included the friction caused by the front wheels rubbing against the eye hooks that held them in place, and the lever arm's length which changed the force output of the mousetrap. We solved the wheel problem by using 2 wheels that were spread out in the front of the car, away from the car as a whole. The lever arm problem was solved by removing the elongated lever arm that we had previously added. This taught me that even the smallest changes can make a huge difference as each part of the car built on the parts previous to it. 

C. If I were to do this project again, I would have started without the use of an elongated lever arm, and I would have built wheel designs that would minimize friction. I would also use a chassis that had a lot less mass and would therefore be moved more easily with the same force.  

Unit 5 Blog Reflection

What I learned this unit:

Work is a force applied over a distance.
Work= Force x Distance( force and distance must be parallel to have work)
Unit for work is in Joules (J)
Power = Work/Time
Unit for power is in Watts (J/s) or Horsepower (746 watts)
Kinetic Energy (KE) is the energy of movement and can be found with the equation KE= 1/2mv^2
Change in KE is equal to work.
Potential Energy is the energy an object has at some height and can be found with the equation PE=mgh
KE and PE are inversely related.
When an object is at rest it has no KE, but if at a height it has PE.
Energy is never created or destroyed, only transferred into something else (heat, sound etc...)
A simple machine is something that makes work easier, you are still doing the same work but it feels easier due to the fact that you use less force because of increased distance. 
Examples are Ramps, Levers, and Pulleys
Work in = Work out
Machine Efficiency= (Work out/Work in) x 100
In this unit, I had trouble with the concept of potential energy, but after a short time I mastered the idea.

My problem solving skills, effort, and learning:
My problems solving skills remained about the same as this unit went on, I simply started to see problems in a different way. My effort has been a bit elevated in this unit as I was working with concepts I had never seen before. My goal for next unit is to keep up strong effort and contribute more to the class. 
My previous goal of trying to work harder on having better effort has worked and I felt that I was trying harder in this unit than before.
This unit helps me understand another reason for why Newton's Cradle works. 

Simple Machines Resource

This video was very helpful review as it applies exactly to what we have learned in class. This video was made by the creator of the textbooks that we use and therefore uses basically the exact terminology that we use in class. I would recommend this video for anyone who is just learning about simple machines or to anyone who wants to review.

Work and Power Resource

The above video provides a perfect example of work and power and the differences between them. This helps me understand the concepts because lifting weights is something I do every day. The only concept that they left out from the video was that the force and the distance must be parallel to be classified as work. But it does provide the basics of work= force x distance, and the fact that power is work over time.

Unit 4 Blog Reflection

Things I learned this Unit:

Rotational Motion

Tangential speed- the distance an object covers in a given time. Depends on radial distance.

Rotational speed- the amount of rotations or portion of a rotation an object performs in a given time

Gears: Same tangential speed, the smaller gear will have to have a faster rotational velocity to account for the equivalent tangential speed.

Example- 8 teeth vs 4 teeth. Smaller gear will have twice the rotational velocity as the bigger one because it has to rotate 2 times to go the same distance it takes the bigger gear to rotate once.

DIFFERENT RADIUS FROM AXIS OF ROTATION= DIFFERENT TANGENTIAL VELOCITY

Rotational Inertia + Conservation of Angular Momentum

Rotational inertia- property of an object to resist changes in the spin. Distribution of mass affects RI. Easier to spin= less rotational inertia, harder to spin= more rotational inertia. 

The greater the distance a mass is from its axis of rotation, the more rotational inertia it will have.

Angular momentum before= Angular momentum after

RI x RV before= RI x RV after

A hoop will have more rotational inertia than a steel ball because its mass is further from its axis of rotation, it will therefore lose a downhill race. (same goes for frozen water bottle vs water bottle)

Torque and Center of Mass

Torque- something that causes a rotation, = Force x Lever Arm

Lever arm- the distance from an object's axis of rotation. 

When an object is balanced its counterclockwise torque is equal to its clockwise torque

Center of mass- average position of mass

An object will fall when its center of gravity is outside of its base of support

Examples of torque + center of mass problems:

Why are football players told to keep their legs bent and shoulder width?

To widen their base of support and get their center of gravity closer to the base of support, they will then have to be pushed harder to get their center of gravity outside of their base of support and fall.

Large wrench= more torque

10 N ball rests on one end of a meter stick with a 1m lever arm. How much must a ball on the other side weigh if it is 5m away from its axis of rotation?

10 x 1= 10

10/5= 2N

Centripetal Force

Centripetal force is a center seeking force

Centrifugal force does not exist

Why are racetracks banked? 

So that they can have more centripetal force from the x component of the support force coming from the track.

 

In this unit I had difficulty with the concept of the racetrack being banked, but after being shown the force vectors I felt completely fine with the subject. I overcame this difficulty by learning to think of force vectors whenever provided such a picture. 

My Problem Solving Skills, Effort, and Learning

Throughout the unit my problem solving skills improved by learning to think of things in different ways such as in force vectors or as in centripetal forces interacting with objects in the world. My effort in the class has been fairly consistent with a few dips in effort due to the fact that I grasped the material sooner than classmates and waited for them to see the reasoning behind a problem. 

My goal for next unit is to have my effort back to where it was before.

My previous goal of not procrastinating has improved greatly and I often feel better prepared for class.

This unit helps me understand why in football I have to keep my legs spread out and my knees bent as to not be hit over so easily. 

                                                         My group's unit podcast

Meter Stick Mass Blog

The above image includes the pictures for step 1 parts A, B, and C.
A. The equations that we used for our initial plan are as follows:
Torque= Force x Lever Arm
Torque Clockwise = Torque Counter-Clockwise (when balanced)
W=mg
Our initial plan was to multiply the mass of the added weight by 9.8 to give us the total weight added to the ruler. We would then find the torque on the side of the weight (we'll use counter-clockwise torque to describe this) by multiplying the added weight by the distance from the pivot point (Lever arm, 30cm).
Since the center of mass of the meter stick itself wasn't changed by adding weight, its center of mass remained at 50 cm. We then found the distance to the pivot point from 50cm and found that it was 20cm for the clockwise lever arm. We did not know the weight of the meter stick, so we plugged in x for that.
The Clockwise torque = the Counter-Clockwise torque when balanced, so we set the two equations of (0.98N)(30cm)= (X)(20cm).
We would then solve for the weight and convert the weight to mass by dividing it by 9.8.

The above image includes all the work that I did in step 3 describing our procedure.
B. Our initial plan worked.
Balancing point was at 70cm, the lever arm of the weighted side was 30cm, the added weight was 0.1 kg, which weighs .98 N. The center of mass of the meter stick was at 50cm. the lever arm from the center of mass of the stick to the pivot point was 20cm. Our final mass of the meter stick was 150g.
C.
For the measurements we took see part B.
Our initial plan worked to solve the problem. When things are balanced the Counter-Clockwise torque will equal the Clockwise torque. The center of mass of the meter stick was unchanged throughout the whole lab. We remembered that when we found the weight of the meter stick we needed to convert it to mass by dividing it by 9.8. The actual mass of the meter stick was only 0.8 off of what we had calculated.
D.

Center of mass/ Center of gravity resource

The above video is really helpful to understand the concept of Center of Gravity. It provides physical examples of how a person's center of gravity can affect what they do every day. This video gets to the point quickly and is very helpful for people who are struggling with the subject, or people who need to review it. Thought the quick speed of the video may cause them to leave out a few details about center of mass and such.

Angular Momentum Resource

The above video concerns Angular momentum and how it relates to rotational motion. This video touches on everything that we have talked about (it was made by the same guy who wrote our physics books). This is a really good video to watch if you are having trouble with the concept of angular momentum or if you are just learning. (I used this video because all of the other videos were for AP physics that I found and had a lot of different formulas).