Top Ten Concepts Of Physics

10. Inertia
Inertia, as defined in Newton's First Law, is a concept that states that an object will continue in its current path at a constant velocity, or remain at rest, unless acted on by an outside force. This means that without someone kicking it, a rock will always remain on a sidewalk. When someone kicks it, the rock will continue in the same direction at the same speed until something slows it down, speeds it up, or changes its path.
9. Friction
Friction is a force that occurs when two objects interact. When our rock rolls along the ground, it is constantly interacting with the ground, which induces a a push in the direction opposite of the rock's direction of travel. This push is known as friction.
8. Conservation of energy
The conservation of energy in the physical world means that energy cannot ever be created or destroyed, only have its form changed. When our rock rubs up against the ground, it experiences friction. This friction causes the rock to lose some of its initial energy, and give it to the ground. Some of the energy, does not go into the ground, and it is given off as light and heat. This might not noticeably warm the rock or the ground. It might not give off any visible light either. However, it is there.
7. Potential energy
Potential energy is an object's energy respective to its surroundings. If the rock were on the edge of a cliff, it would have a high potential energy, as it could fall off the cliff and create kinetic energy. f it fell off this cliff, after 10 meters it would have less potential energy, as it would not be as high up. If it had a mass of 50 grams and a height of 100 meters, it would have a potential energy of 49 000 joules at the top because potential energy equals mass times the acceleration of the object times the object's distance from the ground.
6. Kinetic energy
Kinetic energy is the energy of motion. An object's kinetic motion can be determined by squaring its velocity, multiplying that by its mass, then dividing that number by 2. I an object isn't moving, its kinetic energy is zero. If the rock was dropped off the cliff, it would have a kinetic energy of 24 500 joules after 50 meters. This is because the potential energy plus the kinetic energy of an object always equals the initial total energy of the object, as long as it has not stopped.
5. Gravity
Gravity is a very weak force, being many times weaker than the next weakest fundamental interaction, the weak nuclear force. However, it is the only one of the four that has an impact on our everyday lives. Gravity keeps us secured to the Earth because the Earth is very large compared to us, and we are close to its center. The equation for gravitation is g equals the product of the two masses of the two interacting objects times the universal gravitational constant, or G, divided by the square of the radius between the two objects. The g for Earth is approximately 9.8 meters per second squared.
4. Longitudinal waves
Longitudinal waves are waves that travel in a certain direction, or appear to do so. The frequency of the waves going one way is different from the frequency of the waves going the other way. This seems to us as if the waves travel in one direction or the other.
3. Standing waves
Standing waves are waves that do not appear to travel, but simply oscillate. This happens because the waves going one way have the same frequency as the waves going the other way, but in the opposite direction. Thus, they appear to go up and down in place, instead of traveling as longitudinal waves do.
2. Bernoulli's principle
Bernoulli's principle states that as a fluid's pressure increases, its velocity decreases, and vice versa. This can be observed in a soda bottle. If the bottle is under pressure because it has been shaken, it will travel very fast if it blows the cap off, then will slow down as its pressure is relieved.
1. Coanda effect
The Coanda effect states that fluids that travel over a curved surface will tend to conform to the curve of the surface. This helps airplanes generate lift. The air goes over the curved surface, increasing its velocity in order to get close, but not to the same point as, the air that goes under the wing. The increase in velocity of the air that goes over the wing causes its pressure to drop due to the Bernoulli principle. The pressure difference between the bottom and top of the wing pushes the wing up, giving the plane lift.

Revision of photo project

This photo demonstrates both Newton’s Second Law and Newton’s Third Law. Newton’s Second Law states that force equals the mass of an object times its acceleration. The mass of the object may vary, but the acceleration at a certain point will always be constant, ~9.8 meters per second per second on Earth. It also displays Newton’s Third Law. While the earth’s gravity pulls on the hat, with an acceleration of ~9.8 m/s^2, the hat also pulls on the Earth. The acceleration due to gravity on the Earth from the hat is equal to the hat’s mass times the universal gravitational constant, ~6.67 times 10 to the -11th Newton-meters squared over kilograms squared, over the radius of the circle with a diameter the length of the distance between the Earth’s center and the hat’s center. The hat will have all of these variables equal to the Earth’s, with the exception of mass. The hat’s mass is much smaller, so it will cause less acceleration due to gravity on the Earth than the Earth causes on the hat. Thus, the hat will fall to the ground, while the Earth will barely budge from its orbit.

Electricity and Magnets

In this chapter, we studied magnets and their effect on electricity. We discussed how magnets work, how the Earth's magnetic field is created, how magnets have poles, how electromagnets work, how magnets affect electrical fields, and how this can be used to power objects.

In this chapter, we discussed how magnets work. 

In a magnetized object, the domains of an object, the spin of its atoms, become aligned. The domains of a magnet determine the poles of the magnet are aligned. How aligned the domains are affects the strength of the magnet. If a person were to stick a paper clip to a magnet, that paper clip would be less magnetized than a neodymium supermagnet. The domains of an object can be aligned in several ways. One is shock. Aligning a piece of potentially magnetic metal with a magnetic field and striking it will cause some of the atoms to become aligned with the magnetic field. Another way is constant magnetization. If a strong magnet is constantly left near an unmagnetized magnet, the unmagnetized object will become magnetized in the same way as the strong magnet over time. Because of this, shipboard magnets are specially calibrated to avoid being attracted to the ship, and strong magnets must be kept away from some equipment that relies on magnets, such as computers and pacemakers. Only three metals, and compounds containing these metals, can be magnetized. These are iron, nickel, and cobalt. Other objects cannot be magnetized.

Magnets have magnetic fields because of poles. They have poles because of how its domains are aligned. If a magnet's domains are aligned, the magnetic field will go from "South" to "North" inside the magnet, and from North to South outside the magnet.

 The names North and South come from the Earth's magnetic field, as that is how the charges flow there. Thus, it became the custom to call the directions North and South. Different poles of a magnet will attract each other, and like poles will repel each other. Compasses work because they align to the Earth's magnetic field. The South pole of the needle will be attracted to the magnetic North of the Earth, while the North Pole of the needle will be attracted to the magnetic South pole of the Earth. Magnetic fields are strongest when they are perpendicular, because they are able to block the object fully and slap it aside. The field is weakest at the poles, because the field cannot block the object, and allows to pass.

The Earth's magnetic field works because the core of the Earth is solid iron, causing a large magnetic field around the Earth.

This magnetic field is important because it repels cosmic rays which cause cancer. At the Equator, the field slaps the rays aside, preventing them from getting to the surface. At the poles, the field cannot block the rays, which are visible as the aurora borealis and aurora australis. However, this means that a person at the North pole has a higher chance of getting cancer than a person at the Equator.

Electromagnets work by running an electrical current through a piece of metal. Normally, this metal is unmagnetized. However, running a current through it allows it to become a very strong magnet, as seen here.

The current causes a fluctuation in the magnetic field, causing the domains to become temporarily aligned and making the magnet very strong. 

The opposite is true as well. If a magnet is ran through or past an object that is also magnetic, the object will have a small voltage induced in it, which in turn will induce a voltage, allowing the wire to power an object. 

As seen in the picture, the magnet must move to induce a voltage. If it does not, it will not cause anything to happen.

Generators use a similar process to create power. A person or machine turns a crank which is connected to a magnet with a coil of wire wrapped around it. This magnet and coil is near another magnet. When the crank is turned, the magnet and coil spin. This causes fluctuations in the magnets' magnetic fields, which causes a fluctuation in the wire's magnetic field. This induces a voltage in the wire, which in turn induces a current in the wire. This creates power, which allows the generator to power objects that need it.

Motors and transformers work in reverse of this. The coil of wire is near a magnet, and has current run through it. In the motor, this causes the coil to spin, as it is made to only receive current at certain times to allow it to spin. In the transformer, the coil is near another coil. The first, or primary, coil is wrapped a certain number of times around an object. The second, or secondary, coil is wrapped a different number of times. If it is wrapped more than the primary coil, it is a step-up transformer. If it is wrapped less than the primary coil, it is a step-down transformer. The primary and secondary coils are placed close to each other, and current is run through the primary. This causes a fluctuation in the secondary coil, which causes it to receive a voltage different from the primary coil's voltage, which induces a current different from the primary coil's current. However, the primary's current multiplied by the primary's voltage equals the secondary's current times the secondary's voltage. This process allows an object to receive more or less voltage or current if it needs it. This prevents a 12 V laptop from frying from power taken from a 120 V outlet. 

A video of transformers and generators can be seen here.

This unit was not too difficult for me. I found that it built on the last unit quite naturally, and used what I learned there in this section. While my knowledge of the workings of these concepts improved, I felt that it made more sense coming after the last unit than any other two sequential concepts this year.

Photo Project

This photo demonstrates both Newton’s Second Law and Newton’s Third Law. Newton’s Second Law states that force equals the mass of an object times its acceleration. The mass of the object may vary, but the acceleration at a certain point will always be constant, ~9.8 meters per second per second on Earth. It also displays Newton’s Third Law. While the earth obviously pulls on the hat, with an acceleration of ~9.8 m/s^2, the hat also pulls on the Earth. The acceleration due to gravity on the Earth from the hat is equal to the hat’s mass times the universal gravitational constant, ~6.67 times 10 to the -11^th Newton-meters squared over kilograms squared, over the radius of the circle with a diameter the length of the distance between the Earth’s center and the hat’s center. The hat will obviously have all of these variables equal to the Earth’s, with the exception of mass. The hat’s mass is much smaller, so it will cause less acceleration due to gravity on the Earth than the Earth causes on the hat. Thus, the hat will fall to the ground, while the Earth will barely budge from its orbit.