Gun Control: Momentum

Photo by Phillip C.

There has always been the rumor of bullets falling from the sky. That is, another person shooting a bullet in the air at a high angle (say, 45 degrees) and the bullet coming down miles away and landing on some poor, unsuspecting soul. The major point of this discussion, though, is would that bullet kill someone? We can find this using the theory of momentum and a little bit of research. The impact time of the bullet would be roughly.0014 seconds, and do some research on the forces it would take to kill a person, preferably by hitting their skull.

Take this situation: There is a young boy gun hunting on earth. He is hunting with a 9mm handgun. He decides to be irresponsible, lifts his gun 3 meters off of the ground, and fires two shots: one straight in the air, and one at a 45 degree angle. The bullet's massis 7.45 grams and it has an initial velocity of 366 m/s. The terminal velocity, or the maximum speed a bullet can travel, is about 166 ft/s. Assuming that the acceleration of gravity is 9.8 m/s^2, would any of these bullets have the force necessary to kill a human? Calculate please, don't assume.

Harmony: It's all physics!

Picture by KMLA Orchestra

Music is beautiful, emotional, and enjoyable. It also becomes extremely complex. Even looking at the basics of things such as music theory, the average viewer can become as lost as a first grader trying to learn Advanced Calculus. But let's try and simplify music a little bit first.

To say it bluntly, music is simply variations of pitch and volume. Where it gets complex is when you start adding things such as harmony. Simplified, harmony is when two or more notes are played and they simply sound nice together. Harmony is used in many forms of music, so chances are you know what it sounds like. But what creates this sound when looking at it from a physics perspective?

In physics you learn(ed) that different notes have a related frequency. From a physics point of view, what correlations do two harmonizing notes have with each other when viewing their frequencies? Are there any specific formulas or ratios that make a tear-jerking or powerful chord? Do some research on harmony and share any ratios, formulas, or facts on harmony. ALSO, see if you can find a visual representation of harmony at work, preferably a graph of the waves.

On a Higher Note...

We have all seen it in the movies: a woman belts out a loud, high pitch note that can shatters the glass in the entire building, from the wine glasses to the windows.  But can a voice really reach a frequency high enough to shatter glass?  Glass has a natural resonant frequency which is the speed at which it will vibrate if disturbed by a stimulus such as a sound wave.  However, not all glass has the same natural resonance.  Wine glasses are especially resonant because of the goblet shape which is why, when struck, they emit a pleasant, ringing sound.  It is at that ringing note a singer must reach in order to shatter the glass, vibrating the air molecules around the glass, causing the glass to vibrate as well.  If the corresponding note is sung loud enough, the glass will eventually vibrate its self into smithereens.  But what is that frequency a singer sings to vibrate a wine glass and just how loud would she have to sing to make it shatter?  Also, what else would contribute to making the glass easier to break?  Research the idea and tell me your findings and thoughts.

Helicopters: A Spin on Physics

picture: KNOWN MALTA by Peter Grima

The first early record of a design similar to the helicopter was that of Da Vinci during the Renaissance period. A original concept of having a structure lift off the ground and hover in mid air with personnel on board. Many had thought the idea absurd and impossible, however in 1904 the first helicopter flew and a better more successful version the German Focke-Wulf Fw 61 flew in 1924. The helicopter is very complex and has much improved over the decades. Modern choppers, as many call them, such as the AH64-A Apache, the AH-1 Cobra, and the MI-24 Hind have been suited with top of the line technology and loaded with weapons for military use. Even though many are shaped different and are of different sizes they all run under the same basis for flight. They each have a rotor atop of the platform that rotates to thrusting the air above it downwards to produce a counteractive push upwards on the chopper. What is it about a helicopter that keeps it stable? Wouldn't common sense tell you that this piece of rotating metal would loose control and send it's occupants to theirs deaths? Do some research and see why the helicopter is able to fly the way it does? What are some interesting facts about them? How can they be useful and name some of the ways they have been used and where. I look forward to your comments

Waves: Refraction, Diffraction, and Interference

Refraction of light through glass. Photo by Joost J. Bakker.

Refraction is the bending of a wave as it its speed changes (usually as a result of going from one medium to another). Light provides an excellent example of refraction as it passes from glass to air or from water to air. However, other types of waves can refract as well. Consider a sound wave... ... Can sound refract? Do a little poking around on the internet. Can you find any descriptions of physical phenomena that can be explained by sound refraction?

Diffraction is the bending of light as it passes near an edge. In class we saw how a human hair can diffract a beam of laser light to form an interesting pattern. Look up the term "diffraction grating." What is it and what it is used for?

Interference occurs when two or more waves occupy the same space at the same time. There are many animations and simulations available online to help to visualize wave interference. My favorite is the virtual wave table on the phet site. Search around and post a link to a site you find useful.