## Potential and Kinetic Energy

Kinetic energy – (KE= (1/2)mv^2) The energy of motion. Kinetic comes from the Greek word Kinetikos which means motion. If and object is in motion, it has kinetic energy

Potential energy- (PE= mgy)  The energy given to an object by a system. The Potential energy of an object depends on its position relative to its surroundings. If an object has the potential to move it has Potential energy.

The Potential and Kinetic energy of an object will always add up to the total energy of the object.

In the picture above, the ball has potential energy when the girl is holding the ball and kinetic energy just before it hits the ground. From the point she lets go to right before it hits the ground the ball has potential and kinetic energy. As the ball falls the potential energy decreases and the kinetic energy increases. At any point the kinetic and Potential energy always equals the same number.

## Newtons Three Laws

First Law- “Law of Inertia”- an object at rest will stay at rest and an object in motion will stay in motion till a force acts on it.

For example the only reason why a pop fly (in baseball) comes back down to earth and not keep moving on a linear path into space is because gravity (a force) acts on it, changing its path into a parabola. Moreover, an apple at rest (sitting on a counter) will only fall to the floor if you act on it pushing it of the counter.

## Cup Phone

Why and how does a cup phone work?

First of all for those of you that don’t know what a cup phone is, its two cups connected with some yarn, making a “communication device” (phone).

A cup phone works using the vibrations of your voice. Sound is made up waves that move through mediums, so when you speak, waves of sound are projected throughout the room, building on top of each other and canceling each other out. When you speak into the cup the waves of sound build up on each other and start to vibrate any matter around it (the cup). The vibrations of your voice travel through the cup, then down the string and to the other cup where the vibrations expand through out the cup and become audible.

When making a cup phone there are three important details you need to make them work.  First, you need to make sure the yarn, between the cups, is as tight as possible, not letting the string have any slack. Two, to make the cups work ideally add two paper clips to the ends of the string, inside the cups, to help transfer the sound waves better. Lastly, three, don’t let the string bend around corners or make contact with anything else, for the best sound quality.

If you want to make a three, four, etc. way call add another string attached to another cup. Make sure the intersection between lines is midway of the one your connecting the extra line two.

## Vectors

Vectors are composed of direction and magnitude. Vectors can help describe things like acceleration. When an object only has magnitude or direction like speed its called a scalar. Vectors can be practical in a real world task, like a boat crossing a river. You have to add the river’s vector (direction and magnitude) and the boat’s vector.  The result of the two vectors will show the boats direction and speed as it crosses the river.

In find the final vector’s direction, there are many diffident ways to find it, that depend on the initial products. There is the Tail to Tip method, were the tip of the first vector touches the tail of the second vector. There is the Parallelogram method, were the first two (product) vectors create the bottom of the parallelogram and the last one (resultant) extends to the opposite end of the parallelogram. The parallelogram method only works if the first two (initial) vectors are starting form the same point  (origin). The last vector also starts from the same origin and lays across to the other side of the parallelogram.

Vectors that make a right angle can be solved using Sine, Cosine, Tangent. (SOHCAHTOA). If Vectors  don’t create a right angle (like the picture below) you would have to separate each vector and find its X and Y components and then add all the X’s and all the Y’s. Once you have found the Sum all the X’s and Y’s you would have to find the Tangent of the two numbers to find the final vector’s direction and magnitude.

## Light

Can an object travel faster than light? Well its actually relative to where the light is traveling. An object can travel faster than the speed of light. Light travels at different speeds in different mediums. An electron can move faster than light in the medium of a diamond. The misconception that nothing can go faster than the speed of light only apply’s to C.          C = 299,796,000 m/s. C is the speed of light in a vacuum

## Reflection

The picture below show how light can reflect. The beam of light reflects off of the surface of the water. The angle of reflection is smaller than the angle of incidence so the beam of light gets reflected internally. Because the density of air and water are different (light travels at diffident speeds in them), when the light reaches the edge of one medium, depending on the angle, gets internally reflected or bends into the new medium.

## Gravity

Going down!

the reason why all objects fall toward earth is because of something called Gravity. Gravity on Earth accelerates all objects at 9.81 m/s^2 until they hit terminal velocity, when the object acceleration becomes 0 due to air resistance, falling at a constant speed. People travel 120 mph during terminal velocity.
Gravity’s affect on objects is different in different places in the universe. the gravity on Jupiter pulls on objects a lot stronger giving them a higher acceleration.

## Flight

Have you ever seen a bird land?  As it spreads its wings increasing its drag, slowing the bird down to a swift stop.

There are four main things you must know if you want to fly.

Thrust, Drag, Gravity, and Lift

Thrust, the opposing force of drag, is created by the power of the object, either the jet of an airplane or the figure eight motion of a bird flapping its wings. If the thrust of the object is greater than the drag, the object will accelerate and  if the drag of the object is greater than the thrust the object, the object will slow down.

Drag is the force exerted on an object that moves through some type of fluid, either air, water, or even maple syrup.  Drag increases if the surface area of the object increases, if the object increases speed, and if the viscosity of the fluid is higher.Like the example I gave before, when a bird prepares to land it widens it wings making them larger, increasing its draft, slowing the bird until it gently lands  on the ground.

Gravity, affecting everything in universe, play a key role in flight. Gravity pulls the object toward the earth, causing the object to create more energy to stay in flight.

Lift is the force that opposes the weight of the object being pulled down by earths gravity and perpendicular to the drag of the object. Lift is caused by the enlargement of the bottom part of a bird’s or plane’s wings. Lift  becomes higher if the object mover faster, if the bottom area of the wing is enlarged, and if the fluid is thicker (having more viscosity).