Tuning Fork and Palm Pipe Lab

CRITICAL INFO:

• Waves transfer energy through a medium
• Velocity of a wave is CONSTANT
• Transverse Wave = movement of wave is perpendicular to velocity (jump rope)
• Longitudinal Wave = movement of wave is parallel to velocity (like Dominos)
• Standing Wave = stationary wave -- remain in constant position
• No net energy
• Only occur at certain frequencies (shakes/second) -- Harmonics
• Harmonics = Frequency at which standing wave occurs
• Wind Instruments: only odd harmonics occur because sound must escape
• Even harmonics do not exist
• Equation: Velocity = (Wavelength)(Frequency)
• REMEMBER: wind instruments go by 1/4

** Guitar strings are an example of transverse waves

Tuning Fork Lab: 

In the tuning fork lab, we were able to record the note that each tuning fork emitted, and from there derive several things leading up to defining what exact note it was. Though the Vernier graph that was produced from the recording, we were able to see an FFT graph similar to the one in the picture on the side. By looking at the graph, we were able to analyze the graph and see what harmonic we actually hear (amplitude).

Plugging in that frequency to the Wolfram Alpha website, we were able to pinpoint what exact note and key the sound was. 

** Note: the graph shows that the fundamental frequency is 250 Hz because the that is the lowest in which a standing wave occurs for THAT SPECIFIC MATERIAL. The following numbers are multiples of 250, serving as the 2nd, 3rd, 4th, etc. harmonics. 

 

Light & Optics Real World Connection

Light and Optics: Refraction!

When light passes from one material to another, the path of light must bend to the path of least time, or in other words, fastest route - this is what defines Refraction (bending). 

The Law of Refraction is: Sin0i = nSin0r

What the law of refraction simply mean: Sin(angle of incident) = n(index) * Sin(angle of refraction)

We get the coefficient of n(index) through a separate equation, but it symbolizes that the speed of light will ALWAYS slow down when moving from air through another material.

In the example below we get to see REAL LIFE INVISIBILITY!!

Inside the test tube is oil, and inside the beaker is oil, but the bottom of the test tube is invisible!! This is because light does not need to bend that much or refract due to the similar indexes (alike substances).  Because the beaker of oil has exactly the same index of refraction as the test tube of oil, the light will neither reflect nor refract  between the test tube and beaker. Therefore the bottom of the test tube will appear to be invisible.

Permanent vs. Temporary Magnets

Standard 6.3 Explain how objects like earth and metals can be permanent or temporary magnets.

Domain of object that is
SOMETIMES magnetic

Why are some materials more magnetic than others?

Different objects have different sets of domains, or group of atoms, that determine whether the object is magnetic all the time, sometimes, or never. If an object is always magnetic it means that its domain is lined up and that the electrons are all moving in a uniform motion. This then causes there to be a magnetic field because we know that moving charges = magnetic field. This uniform magnetic field is the strongest force and causes the object to be magnetic ALWAYS.

Objects like paperclips and paper on the other hand contain different domains. A paperclip is magnetic sometimes because it's domain is composed, but not lined up (in the visual above you can see that the sets of atoms are paired but are not in order). This causes their to magnetic fields rotating in different directions, and minimizes its magnetic force. Paper on the other hand is NEVER magnetic. Its domain is scattered completely and contains no magnetic-domain. 

The iPad: What is it really?

This weeks lab on the Lemon Battery showed us the connection between ions and the transfer of energy. We were able to make our own circuit (transform energy to different uses like light, heat, motion, sound, etc.) by using a penny and nail. The acid in the lemon provided for the electrons while the between the pennies' negative charge and the nails positive charge forced electrons to flow (like the iPad battery) through the circuit.

But how does it apply in REAL life? The iPad! For us SI students, the iPad strikes close to home and now we will be able to see how its battery really works!

The iPad battery uses a rechargeable lithium polymer battery. The iPad is actually unique in its use of lithium polymer battery because most laptop batteries are actually made of Lithium-ion, a much less moldable chemical. In the photo, you can see that the battery is actually shaped around the iPad, causing it to be larger and therefore hold more ions for recharging and use. 

So how does it work? The lithium ions move back and forth from the negative electrode to positive electrode during discharge. As the battery is charging however, the electrons move back and forth. This is voltage (to give charges potential energy). As more and more voltage creates a "mountain," then the charges are organized and energy is transferred/stored. 

Projectile Motion

To find out the meaning of a "projectile,"we used the example of shooting a basketball. Using the Vernier Video Physics app on our iPads, we were able to film the entire course of the ball; from being released by the persons hand to hitting the floor. In this lab we not only learned how to utilize the video app but also how to dissect the different aspects of an object that has been projected or thrown, including its velocity and acceleration. 



At the top of the graph below, we were able to find the acceleration of the ball due to its slope. 
- Change in Y(meters) / Change in T (time) = acceleration 

- Slope is NOT constant

At the bottom of the graph, we were able to find the peak of the balls flight; the maximum height. When the line passes through the X-axis, that is what represents the moment in which it has reached the max point. 

The top of this graph (the red line) represents the X-Dimension (horizontal). The slope of this line is the Vx (velocity). Vx is constant and therefore is always positive.  


The bottom of this graph (yellow line) represents the velocity constant as well. Though it appears to be inconsistent, that is only because it is zoomed in so much. 












To tie all of the components  in, 
we used whiteboards to draw out all of the ideas and concepts we discovered.
1. Projectile motion is when the only force acting upon the object is Force of gravity (Fg).
2. An objects acceleration in the vertical direction is due to gravity and is independent of its mass.

Forces in 2-D and Circular Motion

The Big Questions:

1. How do forces cause objects to move in circles?

In order for objects to move in circles, there needs to be a force towards the center of the circle. In our lab, we turned on the hover discs therefore extracting the force of friction. Attached to the hover disc was a string that was being held onto by a person. Acting as the center of the circle/orbit, the person exerted a force on the string and by pulling it towards them, caused the hover disc to circulate perfectly. This a real small picture example with such a HUGE picture idea; it explains how the earth orbits! 

2. What does it mean to be in orbit? How do satellites orbit planets and how do planets orbit the sun?

Just like the hover discs orbited around the person, satellites orbit around the earth and the earth orbits around the sun. Both contain the idea that there is a force toward the center of the objects orbital path keeping everything on course. For satellites, because of the speed the station is traveling at, they are actually in constant free fall. But then why don't they just fall back to earth? Due to the Earths roundness, the space station seems to be orbiting the Earth when it is truly falling but being pulled towards the earths core.