Tuning Fork and Palm Pipe Lab

Tuning Fork and Palm Pipe Lab

During this past week, we learned all about sound waves and harmonics. To get a better understanding of these two things, it helps to know a little more about waves themselves.

Wave: movement of energy in a medium

Wavelength: the length of the wave from peak to peak (meters)

Frequency: How many times the the wave shakes per second

Velocity: the speed in which  the sound wave travels (example-sound travels 343 m/s in air)

Standing Wave: When the wave bounces back and forth at the right frequency to create a wave that looks like it stands still (occurs when there are two or more waves)

Harmonic: the frequency  where each standing wave occurs (multiples of the fundamental wave)

Harmonics Illustration:

Palm Pipe Lab:

In the palm pipe lab we were examining the harmonics of the pipe. Stringed instruments have several different harmonics because they are "closed" and both ends, but because the palm pipe is only closed at one end(and therefore is considered a woodwind instrument), it only has ODD harmonics. Our task in this lab was to find out what musical note our palm pipe played, but in order to do this we had to measure both the length and the diameter of the pipe, and then plug those numbers into an equation.

Picture representing ONLY ODD number harmonics in a palm pipe :

Equation: Length=1/4(Wavelength)-1/4(Diameter)

After we found the wavelength we pugged this onto the fundamental wave equation to find the frequency of our wave.

Equation: Speed= Frequency x Wavelength

After this we plugged our frequency into Wolfram Alpha to find out what musical not our palm pipe played, and I got a B flat. After we all found our notes we were able to follow a chart and play "Twinkle Twinkle Little Star." Who knew simple pipes could create such harmonious music?

Tuning Fork Lab:

In the tuning fork lab we tapped our tuning fork against a softer surface, like the rubber sole of a shoe, and then put it up to the the microphone attached to our LabQuest to measure the waves.

After doing this, the graph we got looked like this:

After analyzing the graph, we discovered that each frequency was proportional/equidistant. This makes complete sense because harmonics are equally spaced, and are multiples of the fundamental frequency. In this case, we found our fundamental frequency( the first harmonic) to be 78Hz. In order to find which harmonic was our peak frequency, we divided 625Hz by 78, because all of the frequencies(because it is a harmonic) are multiples or 78. After doing this we found our peak frequency to be the 8th harmonic.

Light and Optics

Light and Optics

     This images is interesting because it shows what happens with both convex and concave reflections. This is very similar to when we looked at our reflections in spoons at the beginning of the unit.

     The top half of the pot is similar to that of a concave mirror, and just as when we looked in our reflection at the concave part of the spoon, the image is inverted. This all has to do with the way that the light rays(incident rays) bounce off of the mirror and become reflected rays. The light rays bounce off in such a way that the bottom of the image(in this case my face and phone) flip around an become the top of the image. The image at the concave part of the pot is also a real image and is closer to the pot than it is to me.

   The image at the bottom of the pot is more similar to that of a convex mirror. When we looked at our reflection on the back(convex) side of the spoon, our image was upright, and therefore it was also a virtual image. In this case, because of the way the incident(light) rays reflected off of the pot, the image became smaller than my actual head, and is farther away.

(Diagram of incident rays being reflected off of both the concave and convex parts of the pot)

Electromagnetism

Electromagnetism

How is electricity generated my moving magnetic fields?

      The basic concept we learned about the relationship between magnetism and electricity is that moving magnets(changing magnetic field) generate electricity(current and voltage). The best example to explain this concept is a hand crank generator. Inside the hand crank generator there is coiled wire. Coiled wire is essential in this process because the magnetic field surrounding the coiled wire combines to make the magnetic field in the space inside the coil very strong. Also coiled wire makes the current higher and increases the strength of the magnetic field. When we spun the hand crank, we were spinning the magnets and getting the electrons to flow throughout the coil. The moving electrons (electric potential energy) were then turned into a usable source of energy by the resistor (lightbulb).
     
    Before we would get get the current flowing by using a voltage supply, but in this process we are the ones supplying the voltage by moving the magnets. Humans aren't always the ones moving the magnets though. We learned that in generators, different natural resources often move the magnets (water for dams, air for fans) and then that creates the moving current which then creates electricity.

Illustration of how moving magnets now supply the energy:

iPad Battery

IPad Battery

The battery used in an iPad is a lithium-ion battery. Lithium is the element of choice in this case because it is highly reactive, meaning a lot of energy can be stored in its atomic bonds. All of this energy is what allows us to play games, search the web, read books, and utilize all of the features we have on our iPads without the battery losing its charge too fast. The word ion is very important to recognize when talking about these batteries because it has both positive and negative charges stored inside of the cell, and they are unbalanced. When remembering the "mountain" image, it's easier to understand why in the battery, the lithium ions move from the negative electrodes to the positive electrodes (because electrons move "up the hill" towards the positive ions, and this creates energy(before this process happens it is just potential energy among the cells).

(A picture of the path of the protons/electrons)

As shown in the picture below, when the ipad battery in plugged into the charger, the ions are moving from the positive side(cathode) to the negative side(anode). This is happening because carbon has a negative charge, lithium has a positive charge, and opposites attract. When the battery is removed from the charger, the lithium moves back to the positive side of the battery. All of this happens at a higher voltage than most other batteries, allowing us to have such a long battery life when using our iPads because the more voltage, the more potential energy, and the more potential energy, the more active energy being put to use in our iPads.

This is a helpful video to understand how the battery works. Although in this case it shows the battery being put to use in a car, it is the same idea with and iPad.

http://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery.htm

http://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery1.htm

Projectile Motion

Projectile Motion

       In this week's lab we analyzed projectile motion. We did did this by throwing a basketball into the air, and as soon as it left our hands it became a projectile. Because the main idea in this lab was forces in two dimensions, we analyzed both the x(horizontal) and y(vertical) dimensions of the ball. After doing this we concluded that in the x direction the only force acting upon the ball is gravity(a downward force), and that the the ball is moving at a constant speed horizontally in the x direction but not in a constant direction. When we analyzed the ball in the y direction we were able to see that it was accelerating but constantly slowing down.

Here is a visual of the force acting upon a projectile-GRAVITY

(disregard the interaction between the person and the earth)

X-Dimension

This velocity-time graph shows the velocity of the basketball in the x direction. After analyzing the graph with a best fit line, we can see that the slope is zero, meaning that the x-velocity is constant.

In this position-time graph we can see that the position of the basketball in the horizontal direction is changing at a constant rate from its initial position.

Y-Dimension

In this velocity-time graph we can see that the velocity of the ball in the y-direction(vertically) is always accelerating at -10m/s^2 (we get this from the slope) from the initial velocity.

In this position-time graph we can see that the position of the basketball in the y direction(vertical) is in the shape of a parabola because that is literally the path the ball takes in the vertical direction.

Forces in 2D and Circular Motion (Hover Disc)

What does it mean to analyze forces in 2D?

To get a better picture of what a 2D force is, it's easier to know that the sketch of a 1D force is simply a line. So to get a 2D force you must add another line, and when you add this other "line" or another dimension, your force now had length and width. The length and width are represented on the graph by the x and y axes.

How do forces cause objects to move in a circle?

Forces Cause objects to move in a circle through centripetal force. To better understand this process, it helps to know the centripetal means "center-pointing." So while the object is being pulled toward the center through tension force, because it is going at a constant speed, but also accelerating, it remains in a circle. This may sound confusing, but we learned that acceleration doesn't just mean a change in speed, it can also mean a change in direction. So because our object is moving at a constant speed but also changing direction, it is accelerating.

What does it mean to be in orbit?

To be in orbit means when one object follows a "curved path," or moves in a circle around another object, while also being acted upon by centripetal force.

How do satellites orbit planets?

In order for a satellite to successfully orbit a planet, it must be going at the correct constant speed. The satellite is being pulled in toward the planet through gravity. When the satellite reaches its correct speed, centripetal force kicks in to keep the satellite from falling towards the planet, because as weird as it may seem, satellites are always falling. In the lab, when we kept the hover disc moving at a constant speed it's motion remained in a circle. If we were to slow it down, the disc would move in to the center towards us, and we were to speed the disc up we would eventually lose control and it would fly off.

How do planets orbit the sun?

Planets orbit the sun because the sun is the centripetal force acting upon them, very similar to  how satellites orbit around the planets. So each of the planets are falling, and want go in a straight line, but it is the gravitational pull that is preventing them from doing that. So don't ever let anybody tell you there is no gravity in space! And again because their direction is not constant, the planets are accelerating around the sun. Because both the sun and the planets are curved, the planets are falling around the sun, but missing it's surface as it moves in a circle.

Newton's Laws

Newton's Three Laws of Motion

Newton's Three Laws:

First Law: An Object at rest or in motion will continue to be that way unless acted upon by an unbalanced(net) force.

Second Law: Force=(Mass)(Acceleration)

Third Law: For every action there is an equal and opposite reaction

Hover Disc Lab

Purpose: The purpose of this lab was to help us better understand Newton's First and Third laws of motion.

Background: Before starting this lab we learned about all of the forces in nature that can explain and predict what we observe in the universe.

• • Gravitational - Fg - two objects have mass
  • Normal - FN - electrons on the surface of atoms repel
  • Friction - Ff - electrons on the surface of atoms are shared
  • Tension - Ft - electromagnetic bonds are stretched (rope)
  • Spring - Fs - electromagnetic bonds are stretched/compressed (spring)
  • Buoyancy - FB - fluid molecules repel on/in liquid

Procedure: We completed this experiment in total of 10 trials. For the first few trials, we turned the fan on to eliminate friction between our object and the ground. Then for the last few trials we  turned of the fan, making Friction for a factor in our experiment. We did a variety of things, but mostly we either had person 1 or 2 push the disc or stop the disc, or we just let the disc move at a constant speed by itself.

Data: We used two different types of diagrams to interpret our data, Interaction diagrams and Free Body diagrams. Interaction diagrams allow us to see the different types of forces between all of the the objects in our experiment, and a free body diagram allows us to see the forces acting on one of our objects...in this case our disc.

Hover disc is ON. Disc is at rest. Disc had not been pushed.

Hover disc is OFF. Disc is being pushed by person 1.

Hover Disc is ON. Disc is being caught by person 1.

Conclusion: From all of this data, we are able to prove Newton's first law, that an object at rest or in motion will continue to be that way unless acted upon by an unbalanced(net) force. We also prove Newton's third law, that for every action there is an equal and opposite reaction(using the same force). We observe this when the hand stops the disc from moving. Both are exerting normal force, but they are moving in opposite directions.

Real World Connection: Air Hockey

Air hockey is a perfect example of Newton's First Law.In the game of air hockey you have a puck, handles, and a table. The air coming up from out of the table eliminates the friction between bot the puck and your handles. If you were to leave the puck and handles on the table while the table was on, the puck and handles would continue moving at a constant speed forever(or at least until the table's batteries ran out). When you hit the puck with the handle though you are creating a net(unbalanced) force, therefore causing the puck to accelerate.

Fan Cart Lab

Purpose: The purpose of this las was to better understand Newton's Second Law and the relationship between mass, force, and acceleration.

Background:  1) Acceleration is a change in velocity over time

                         2) Acceleration is the slope in a velocity 

Procedure: We had a track with a sonic range finder on one end and a force probe with a metal ring attached to it on the other end which was hooked up to the computer. We completed a total of 5 trials, and for each trial we increased the mass of our cart by adding brass masses.

Data: In order to find the acceleration of our fan cart we measured the slope, because acceleration= the slope. We also analyzed our data using liner fit(y=mx+b) because we were finding the slope.

Here are two examples of our graphed data:

Mass=.5kg - Acceleration=.3773m/s^2

Mass=1.3kg - Acceleration=.1372 m/s^2

After we got the results for all 5 trials, we tried to derive an equation from our data.

Equation Time!

Fnet= m(a)

• F= net force
• m=mass
• a=acceleration 

Analysis: From our data we were able to conclude that net force equals mass times acceleration, and that mass and acceleration are inversely proportional (as the mass increases the acceleration decreases). We also were able to understand the concept of net force, and that unless an object has a net(or unbalanced) force, the object will not accelerate.So an object's acceleration depends on it's mass and the net force it experiences.

Real World Connection:

This lab can be connected to something a lot of us do regularly, and one of my absolute favorite things to do...grocery shopping. If we were to push our cart several times(with the same amount of force) and each time add more mass(more food) to our shopping cart, as our cart's mass increased, our acceleration would decrease each time.