piano

i was playing some Beethoven on my keyboard the other day and realized that there was a lot of physics involved in the music i was making. Each time i pressed down on a key, sound waves were produced and came out of the speakers. These longitudinal mechanical waves moved through the medium, air, to my ear. i played the note A, and remembered that A has a frequency of 440 Hz. i moved down the keyboard and played another A. This note was an octive lower and therefore had a frequency of 220 Hz.

sound2

So tonight i was listening to some kelly clarkson, my favorite american idol, and the music was pretty lound. My dad came into my room and told me to turn it down. so i turned down the volume and the music got softer. I quickly realized that this simple act is an example of physics. As i turned down the volume i decreased the sound intensity. Sound intensity is the sound of power per unit of area (intensity=power/area) Turning the volume knob down on my amplifier decreased power to the speakers and therefore decreased the intensity of sound. This same action also decreased the sound level. Sound level is the loudness. While sound intensity is objective, sound level is subjective.

thank goodness for magnets!!!

this weekend i went on a long hiking trip through the mountains. i only brought with me a water bottle, three matches, a pocket knife, and a compass. about two hours into my trek, i noticed i had no idea where i was and that i was lost. luckily i had my trusty compass!!! the earth has a magnetic north and south pole. (north pole of earth= south pole of magnet and vice versa) when the red needle on the compass points north, it is actually being attracted by the earth's magnetic south pole. the geographic poles and magnetic poles of earth are not at the same place. the angle between them is known as the angle of declination. thanks to the earth's magnetic poles, i was able to find my way.

guitar amps and variable resistors

so i was cleaning up my room this weekend and stumbled across my old guitar amp. as i was looking at it i realized that the amp had a lot to do with physics! We had just learned about variable resistors in class this past week and i noticed that the amp has a variable resistor to control the volume. i learned from the equation that resistance depends on resistivity, cross sectional area, and length. As i turn the knob to increase the volume, the length of the conductive material shortens. This results in less resistance, therefore allowing electrons to flow through at a faster rate. as i turn the volume knob down, the length increases, resulting in higher resistance. The electrons to flow slower and the current is decreased which causes a decrease in the sound output.

sound!

so i was in my room listening to some music trying to think of what i should do for my physics journal. and then i realized, hey! there must be some physics in my speakers playing the music. I was very interested to see how it all worked so i went to my trusty text book to learn more about this concept of sound. Sound waves are longitudinal waves that move through a medium like air. I noticed that my speakers vibrate forward and backward. The speakers are actually causing the air or medium to compress and decompress. When the speaker comes forward the air compresses causing the particles to become closer together. This region is of higher pressure and is known as condensation. When the speaker diaphragm pulls back, is creates rarefraction, or an area with fewer particles and lower pressure.

BATTERIES

Today i wanted to watch the super bowl, so i sat down on my couch and grabbed the remote. When i tried to turn on the tv; however, it wouldn't go on. I pushed and pushed, and nothing happened. I was almost ready to give up and not watch it at all, until my sister brought me over a fresh pair of batteries. Batteries are sources of eletric potential energy. The batteries in the remote have a positive and negative terminal (different electric potentials). The voltage of the AA batteries in the remote control is 1.5V. A chemical reaction inside the battery creates electrons. The metal springs in the remote connect the battery's negative and positive ends. The electrons collect on the negative end of the battery, and move towards the positive end. By doing this and completing the circuit, the batteries give the remote control power to change channels.

water faucet and balloon

So today i was playing with a balloon near the kitchen sink and noticed something amazing. I rubbed the balloon on my hair. This caused the initially neutral balloon to gain electrons from my hair through friction, therefore giving one area of it a negative charge. As i brought the balloon near the stream of water, the water was deflected towards the balloon. After visiting the physics home page i was able read up on this phenomenon and understand what exactly was going on. Molecules in water are free to move about and rearrange themselves. The hydrogen atoms are positive, and oxygen atoms are negative. As i brought the balloon near the water, the molecules in the water moved around so that the positive atoms were near the negatively charged balloon. This therefore caused an attraction between the balloon and stream of water.