Sound Principle

• Sound  Principle
  l              Sound is a kind of wave. 
  13.1 Introduction to Wave Theory
  1.       Types of waves
  l              There are two types of waves, transverse and longitudinal. 
  l              When the direction of travel of the wave is perpendicular to the motion of the source, the wave is transverse.
  l              When the travel of the wave is parallel to the motion of the source, the wave is longitudinal. Sound is typical example of this type of wave.
  l              Both types of waves require the action of an oscillating or vibrating source, the motion of the source is called simple harmonic motion.
  
  
  2. Aspects of Periodic Waves
  l             Both types of waves are recurring cycles of the same motion, thus we called it periodic waves. The motion can be represented by the sine wave in mathematics.
  Terms used to descript waves:  
  l              Cycle: a cycle is a complete sequence of motion that repeats itself
  l              Wave-length(λ): wave-length is the length in metres in one cycle
  l              Period(T): period is the time to complete one cycle and is measured in seconds
  l              Frequency: frequency is the number of cycles in a given time, which is measured in cycles per second. The unit is named hertz (Hz).
  l              Amplitude: the amplitude of wave is the maximum disturbance of a wave from it zero point(negative or positive), measured in metres(m)
  
  
  3. Wave Equation
  l             v =λ/T   =>  v =λf  (f=1/T)
  
  
  13.2 The Transmission and Speed of Sound
  1.  Medium Dependence
  l             Sound is a longitudinal wave that requires a medium to travel in.
  l             In air, only possible type of vibration is longitudinal. Air cannot sustain a transverse motion, otherwise air particles will drift off.
  l             The dense areas of air transmitting a sound wave are called compressions and the less dense areas are called rarefactions.
  l             Factors affecting the speed of sound are: the type of medium(gas, liquid or solid), temperature and density.
  l             Generally speaking, the stiffer the material, the faster the speed of sound.
  
  
  2.       Dependence of Speed on Temperature
  l             : v = 332m/s + (0.6 m/s / °C )(T °C)
  
  
  13.3 Mach Number and the Sound Barrier
  
  
  l             When objects (such as aircrafts and cars) get close to or go faster than the speed of sound, a different unit is often used to describe their speed. It has called Mach Number.
  l             1 mach = one time of speed of sound
  l             Subsonic: speed < mach 1
  l             Supersonic: speed > mach 1
  l             Hypersonic: speed > mach 5
  
  
  1.           Sound Barrier
  l             The term “sound barrier” is used in aviation to describe the buildup of sound waves in front of a plane as its speed close to the speed of sound. (The first plane to break the sound barrier was the Bell XS-1 experimental rocket on October 14,1947; the fastest plane in the world is X-43A, which has a speed greater than 7 mach with the best record of 9.7 mach(11000kph))
  
  
  2.   Sonic Boom
  l             When a plane breaks the sound barrier, it will leave a pressure wake behind it. The waves will spread out and move down towards the ground. We will hear it as a loud "boom".
     

The Ethanol-Fueled Cannon Post Lab

1. What are the two baffles in the "cannon" for?
The two baffles are used to provide more surface area for the cannon so that to increase the rate of the chemical reaction which takes place inside the cannon. Further, the mixing of the fuel with the air inside the cannon would be more complete and as a result, we can get a complete combustion of all the fuel and the cannon ball will go further.

2. What purpose did the shaking of the stack of cans have?
The shaking of the stack of cans was right after the injection of the fuel. Its purpose is to mix the hydrogen gas with the oxygen gas together to maximize the combustion. At the same time, ethanol is spreaded throughout the cannon so that the chance of ignition will be maximized.

3. What kind of Energy transformation occurred during the launch?
The (potential) chemical energy is transformed by the combustion, partially to the kinetic energy of the moving cannonball, partially to the thermal energy while heating the air of the cannon, and small amount to the sound energy and light energy as well. Then the moving cannon's kinetic energy changes into gravitational potential energy as it rises and comes back to kinetic energy as it falls(when the shooting angle is not 0); some of the energy is consumed by the air resistance as well.

4. What other kinds of liquids do you think could be used in place of ethanol?
A lot of other kinds of liquids could be used such as gasoline, alcohol, methanol, propane(after compression it could be liquid), etc. because they are all flammable and can produce lots of energy.

5. Apply one of Newton’s laws that is relative to this experiment. Explain.
Two Newton's laws are relative to this experiment:  Accroding to Newton's third law, it states that for every action force, there is an equal and opposite reaction force. When the cannonball is launched forward by cannon, the ball also pushes the cannon backward. This pair of forces are equal and opposite. However, since the cannon is way larger and heavier than the cannonball, it doesn't move a lot.
According to Newton's first law, it states that An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. That's why after the launch, the cannonball is still moving(there is no applied force during this time), it is moving by inertia.

Bibliography:http://www.theteachersguide.com/moredemos.html
http://www.physicsclassroom.com/class/newtlaws/

Famous Cannon

Famous Cannon & Mortars

Dictator - 13-inch Mortar Perhaps the most famous mortar used during the war was the "Dictator." This weapon was a 13-inch Model 1861 seacoast mortar which was mounted on a specially reinforced railroad car to accommodate its weight of 17,000 pounds. Company G of the 1st Connecticut Heavy Artillery, served the "Dictator" at the siege of Petersburg, Virginia in 1864. The mortar could lob a 200-pound explosive shell about 2 ½ miles. The "Dictator" was usually positioned in a curved section of the Petersburg & City Point Railroad and was employed for about three months during the siege.

Swamp Angel - 200-pounder Parrott Rifle In preparation for the bombardment of Charleston, South Carolina, in August, 1863, Major General Quincy Gillmore ordered the construction of a battery in the swampy marsh near Morris Island.  An 8-inch, 200-pounder Parrott siege gun was mounted, under fire from the Confederates, and promptly began firing incendiary shells into the city. This gun, named the "Swamp Angel" continued firing for two days until, on the thirty-sixth round, the gun exploded. But, it had caused a tremendous amount of moral damage in Charleston and went into history as the most famous Parrott gun.  The "Swamp Angel" cannon is now located in Trenton, NJ.

Confederate 7-inch caliber Brooke rifled cannon, triple banded Charleston, S.C. Mounted gun, parapet of Fort Moultrie CREATED/PUBLISHED 1865. SUMMARY Photographs of the Federal Navy, and seaborne expeditions against the Atlantic Coast of the Confederacy, specifically of Charleston, S.C., 1863-1865. NOTES Civil War photographs, 1861-1865 / compiled by Hirst D. Milhollen and Donald H. Mugridge, Washington, D.C. : Library of Congress, 1977. No. 0621 Forms part of Selected Civil War photographs, 1861-1865 (Library of Congress) Modern photographs taken at Fort Moultrie in 2001.

10-inch Columbia smoothbore, rifled and banded by J. M. Eason Brothers J. M. Eason Bros.:  Charleston firm operated by J. M. and T. D. Eason.  James M. Eason, proprietor.  Soon after the capture of Fort Sumter the Eason firm prepared machinery and began rifling a 24-pounder smoothbore for the State of South Carolina.  Subsequently, a portable rifling machine was made which could rifle guns at various distant locations.  The Charleston Mercury of July 20, 1861, reported that "... it has been demonstrated that the Eason gun will throw solid shot or shell, with accuracy, further than any other cannon now in our possession."  By September over twenty heavy guns were at the shop awaiting rifling operations.  (Columbus Times, September 9, 1861)  In November, 1862, Major Childs at the Charleston Arsenal reported that "full three weeks have heretofore been taken by Messrs. Eason Brother in rifling and banding 32-pounder and 42-pounder guns; but that by working at night and on Sundays and distributing the work between Eason and Cameron I hope to be able to finish one gun per week."  (O.R.., XIV, 690)  General Beauregard, on his own initiative and without Richmond's approval, later had several Columbiads rifled by Eason.  This embroiled him in a controversy with the War Department and initially payment on the bill was refused.  Rifling of Columbiads had not proven successful in the past but Eason also banded the guns which made them considerably safer.  Under growing political pressure, the War Department backed down and the bills were paid.  Two 10-inch Columbiads rifled by Eason survive at Charleston.  The one shown is located at Fort Moultrie, S.C. and was used in Battery Bee on Sullivan's Island.

Widow Blakely - 7.5-inch Blakely Rifle "The Widow Blakely" was located about 1 mile north of its current position during the Siege of  Vicksburg, Mississippi.  It was misidentified as a 7.44-inch caliber rifle but inside micrometer measurements of the lands, nearly 1.5 inches wide, show diameters between 7.50 and 7.51 inches. On May 22, 1863, one of "The Widow Blakely's" shells exploded in the tube while it was firing at a Union gunboat.  The explosion took part of the end of the muzzle off, leaving the remainder of the tube intact.  The ragged ends were cut smooth and the rifle was used as a mortar during the rest of the siege (Pemberton surrendered to Grant on July 4, 1863).  It is rifled with 12 lands and grooves in the typical hook-slant Blakely fashion.  After the trimming of the muzzle the overall length is about 100 inches.  Originally the tube would have been about 124 inches long.  It was taken to West Point Military Academy as a war trophy and remained there for ninety-six years until its return to Vicksburg.

Newton's four problems

Isaac Newton, the "Master of Physics", was dealing four types of problems in his life:

• Equilibrium
• Inclined Planes
• Pulley
• Train

Here are the assumptions and the make-up questions for these four problems:

The Newspaper Tower

So here is our group's Newspaper Tower. Even though it is not as high as other groups, but i think the top is very unique from others' (The tape is on top like a flag). Further, I think the base of our Tower is steady; it has the shape of tetrahedron, just looks like the camera stand —— the best friend for photographer. Then we just try our best to roll the rest of newspaper as high as possible while as the same time to make it strong (Then use tape to connect all the cylinder shape newpaper together). However, I think we could change one thing so that it could be higher. We used too much newspaper for the base, I think it is a good idea to reduce the usage of newspaper for each foot of the base and put them at the top to make the tower higher. Though we still need to add more newspaper at the bottom to support the top and the whole weight, the height would still be higher. The only excuse that I give is that we don't want to take the risk of the tower falling down. We want to make sure that it could stand at the first place,  and after that, we didn't have enough time.

The Tower with the "flag"

The physics principle that we applied for this tower is: low centre of gravity so that the tower would be stable. Otherwise, the movement of air would make the tower fall. That means the mass at the bottom should be heavier that the top (That's why we used a lot of newspaper at the bottom). Also, I think, for real buildings, we need to use Newton's second Law so that the building would bear the earthquake or other disturbances.

My favourite skyscraper —— Trump International Hotel & Tower @ Dubai

Night view of Trump International Hotel & Tower

In my opinion, most of the skyscrapers in Dubai are very aesthetic such as Burj al Arab,  Palm Tower.  However, I think, Trump International Hotel & Tower in Dubai, is the most attactive one around the world because of its unique, fantastic appearance. Its top is very beautiful, looks like the tail fin of a shark, and it is very surprising that the central part is hollow (just like two seperate skyscrapers got connected on the top). Though it reminds me the famous skyscaper in Malaysia called Petronas Twin Towers (two building connected by a bridge), I still think this one is way better because its shape is very distinctive than any other skyscraper. Even though it is only 1181 feet high(around 360m) compared to Burj Dubai (the highest hotel in the world with 2684 feet), it looks more like a precious artwork that needs to be protected and enjoyed. Hope  you will love this skyscraper as well.

Projectile Motion - Textbook Pg113 #22, 23, 30