Photo Opp!

Our latest assignment  was to take a photo demonstrating physics concepts for the AAPT Photo Contest. My photo will be entered into the contrived category. I took a picture of my self in a fish tank. The two sides of the tank reflect my image from different angles, which results in the appearance of two virtual images produced. This is because light obeys the law of reflection, which states that the angle of incidence is equal to the angle of reflection. After the light enter the first glass side, it is refracted, and the angle is changed a bit, which results in a slightly differently positioned image on the second side. Flat mirrors produce an image that is upright, the same size, and virtual. The fish tank is a very smooth and produced a specular reflection. A specular reflection is clear and easy to see. The swirls in the picture are from the wall behind the fish tank. I am very proud of my picture in the fact that I was able to produce a picture that reveals several physics concepts.

Electromagnetic Waves

Electromagnetic waves are basically waves of energy caused by a vibration. Based on their wave length and frequency, they are organized on the Electromagnetic spectrum. They usually travel at the speed of light (really really fast).What makes all electromagnetic waves similar is that they can travel through a vacuum, unlike mechanical waves which only travel through mediums.

From: http://www.astrosurf.com/luxorion/Radio/spectrum-radiation.png

The Waves in order of biggest wavelength to smallest.

1. Radio Waves

2. Micro Waves

3. Infared Waves

4. Visible Waves

5. Ultraviolet Rays

6. X-rays

7. Gamma Rays

8. Cosmic Rays

X-Rays

These are very powerful waves that can go through most anything. They are used to see inside people when they have injuries. They are also used at security at airports in order to see into people's bags. Sometimes they are used by astronomers to locate objects not detectable by the human eye. X-Rays can cause cell damage and cancer. This is why radiologists do not stand in the same room when taking an X-Ray of a patient. Lead can deflect this radiation, which is why patients wear lead blankets during X-Rays. Many days of exposure can pose serious risks.

Frequency: (5*10^15)-(1*10^19) Hz

Wavelength:(8*10^-8)-(1*10^-11) m

From: http://www.justcolleges.com/images/bnr_xray-schools.jpg

Infrared Waves

These waves are given off by hot objects, including our own bodies. They are used in television remotes, in heat lamps, and telephones. Night sight goggles or additions to weapons use infared in order to see and criminals can be tracked by looking for infared waves that their body gives off. They also are used in security systems and to track the weather. Infrared waves are used extensively in the military. High settings of infrared directed towards the eyes can harm vision.

Frequency: (8*10^10)-(4*10^14) Hz

Wavelength: (1*10^-3)-(6*10^-6) m

Sources:

http://school.discoveryeducation.com/lessonplans/interact/electromagneticspectrum.html

http://www.darvill.clara.net/emag/index.htm

Using up lots of Energy

Our latest unit is Energy. We have learned how energy is transformed in different processes. We learned how to make energy flow diagrams, identify the system, and calculate work. We also learned how to calculate power, and identifying how the energy is transformed in each problem. We learned how to calculate kinetic energy, potential energy, elastic potential energy, and mechanical energy. For a reflection on this unit, we chose an application and had to explain the system, the energy stored, and the energy transformations. I chose cheerleading basket tosses and used Prezi. In my example, air resistance is negligible.

Energy on Prezi

Photo Credits:

1. www.freewebs.com
2. www.sharonanndance.co.uk
3. www3.wallacestate.edu

Busting Myths and Other Dangerous Activities of Physics

For a creative approach to a lab on forces and Newton's laws, our teacher gave us two myths that are commonly accepted. We were instructed to design an experiment for each myth, trying to disprove it. I worked in a group with Matt, Ford, and Blaine.

Myth One: An object always moves in the direction of the net force exerted on it.

Materials:

1. Baseball

2. Baseball Bat

3. Ford

Procedure:

1. Ford will toss the baseball up in the air.

2. Ford will hit the baseball with the baseball bat.

3. We will observe the baseball until it hits the ground.

Prediction: If it is true that an object always moves in the direction of the net force exerted on it and we observe the tennisball after the bat is no longer applying a force on it, the ball should drop straight to the ground or .

Free Body Diagrams:

1. Baseball bat hitting baseball:

2. After baseball bat has hit baseball, while baseball is still in the air:

Sum of the forces:

1. 

2.

Observations: After the baseball bat was no longer applying a force on the baseball, the baseball did not drop straight to the ground or move backward in the horizontal direction. Despite that the only forces working on it were air resistance and gravity, the ball continued to move forward in a horizontal direction, officially busting this myth.

Myth Two: An object always changes its motion if there is a force exerted on it by other objects. 

Materials:

1. Blaine

2. Ford

Procedure:

1. Ford will run full speed towards Blaine who is stationary.

2. We will observe Ford's movement after Blaine applies a force on him.

Prediction: If it is true that an object always changes its motion if there is a force exerted on it by other objects and we observe Ford's collision with Blaine, then Ford's motion will change after hitting Blaine.

Free Body Diagrams:

1. Ford before colliding with Blaine:

2. Ford when force is applied by Blaine:

Sum of the Forces:

1.

2.

Observations: Ford's motion did not change after his collision with Blaine because the force he applied was greater than the force that Blaine applied on him. This myth is officially busted.

Conclusion:

1. Are there any myths you couldn't disprove? Does this mean these myths are proven?

Though my group was able to disprove both myths, if a myth was not disproved, that does not mean it is proven. The experiment that you picked could have just been one case where it works, while there is another that could disprove it.

2. For each of the myths you "busted", explain why people still believe they are true.

These myths are based off of common sense. For myth number one, this is the case most of the times, however, it is not always true in situations such as projectiles. For myth number two, also seems like common sense, but people forget that if the force applied on the object is too small, it will not affect it.

Video of Experiments:

Physics Carol

So for extra credit, we can write and perform a "physics carol": a song about physics to the tune of a Christmas carol. I wrote mine to the tune of "Here Comes Santa Claus". It is called SOHCAHTOA.


If you have a right triangle that you need to solve
Use my formula and your problems will all be resolved.
It's so simple: SOHCAHTOA, it makes everything better.
With the time you have left over, you can knit a sweater.

You are probably wondering how you can use this
When you are trying to solve a problem in Physics.
In questions with vectors and net forces it can be of use.
Between your sanity and an 'A' you will not have to choose.

My Buddy Newton

We have just finished studying Newton's first three laws of motion. Overall I have enjoyed this unit and liked being able to draw more free body diagrams.

I learned that the first law states "An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force." In other words, when the forces of an object are in equilibrium, the objects will keep doing what they're doing unless a force unbalances the object. The resistance of an object to change is called inertia. Basically, objects are pretty stubborn. Force is a vector quantity (magnitude and direction) that is measured in Newtons. I wish I could name something after myself. To solve equations, you add up all the forces in the Y and the X axis and solve for the unknown. Because the object is in equilibrium (not moving or velocity is constant), it's not to hard to solve for the unknown because the forces add to zero. Where I did have trouble is when the object is at an angle or on a ramp because I kept assuming that the force of gravity was still in the Y axis, instead of shifting the axis, which made the problems nearly impossible to do.

The third law states that when one object exerts a force on another object, the second object exerts on the first an equal force in the opposite direction. Every force (action force) has a reaction force. So, if you're standing on the ground, the ground is also pushing up on you. This concept wasn't difficult for me to understand.

The second law states that for a particular force, the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object. In human-speak, the sum of the forces equals mass times acceleration. It wasn't too hard to plug in the numbers for that, but I was super confused until I realised that the forces were no longer in equilibrium, so I don't solve them the same way. Whichever direction has acceleration doesn't equal zero, it equals mass times acceleration. Once I understood this, I could solve the problems with ease.

Another difficulty in this unit was absence. I got the stomach flu for all last week and had to catch up, so this provided a disadvantage.

Overall, this unit was definitely not the most difficult to understand, though it still provided challenge. I enjoyed the unit a lot.

Vectors Unit Summary

We started out the unit learning about trigonometry. We used SOHCAHTOA to solve angles and sides in triangles. This was a review for me because I've already learned this in my math classes. Next we learned about vector components. I learned that you can find the two components (x and y) using R and cosine or sine. I think that I picked this up pretty easily, but I had trouble knowing when to subtract the angle from 180 based on the quadrant. Where I really struggled was when the vector was no longer at a right angle. It took me a long time to understand this. I had to rework a lot of the problems over and over again, but with the help of my classmates and the wonderful Mrs. Gende, I think I have a better grasp on the concept. Then, we learned about projectile motion. We learned that the horizontal velocity is constant and that the vertical velocity changes uniformly. I understood this pretty well, but again, when we stepped it up a level to projectile motion on an angle, all the formulas changed and I was confused all over again. Then, I figured out that they weren't really changing, it was just a different way of looking at them. Overall, I feel like I have a good grasp on this unit.
Learning about Projectile Motion isn't just important for class but for cheerleading too. In certain tosses, we need to know exactly where the flyer is going to land so we can catch her. Using projectile motion, we can figure this out.