My tuner (No floating things this time, I promise.)

Here is my beautiful combination tuner metronome, which I use to attempt to stay in tune when I play my flute. The little pointer shows you if you are flat or sharp. There is also a little calibration thing in the top left corner that I never took much notice of before this. If you look VERY carefully, it says 440 Hz, the frequency of the sound waves. This means that the tuner thinks that A is 440 hz, or 440 cycles per second. The little calibration buttons allow me to change this (if I really wanted to tune myself to some weird key, I could.) Also, since the period is the reciprocal of the frequency, the period is 0.0023 seconds. The sound coming out of my flute is actually a compression and uncompression of air that travels in waves through the air. So although I'm blowing across the headjoint of my flute to make vibration and sound, this traveling air doesn't actually have anything to do with the sound that echoes around the room. At average room temperature, these waves would be traveling at 331 m/s, but the density of the silver in the flute is much greater than that of the air, so technically the sound travels through the flute itself much quickly than it travels through the air. This means that I could feel the vibration of the flute before I hear the sound itself... if I could hear a difference of milliseconds. Yay! Last blog before Christmas break!

A floating sponge

Yes, yet another blog on floating things. :P Of course, this doesn't mean that I haven't done 2 days worth of physics hw due to 21 hours of robotics competition, 4ish hours of band concert, almost 3 hours of an activity at the zoo I went to with my family, 3ish hours of dinner/partying after the robotics competition, and 20 hours of sleep in 3 days in my attempt to catch up on sleep. Which leaves about 11 hours for hw and eating... >< Missing school = pain...

Anyway, while washing dishes, I realized that the floating sponge meant that the buoyant force of the sponge was equal to the weight of the sponge itself. If I pretend that the sponge mass is 0.25 kg (I hope it weighs significantly less than that, but I'm too lazy to do the math with a stranger number. And I'm not about to weigh the sponge.), then it's weight in newtons is 2.45 newtons downward. This means that the buoyant force is also 2.45 newtons. If the buoyant force is equal to density times the acceleration of gravity times the volume of fluid displaced, and the density of water is 1000 kg/m^3, then you can find the volume of the sponge. This volume would be 2.5e-4 m^3. (Amazingly, this is reasonable sized for a sponge.) The density of the sponge could also be found, since D = m/v. The density of the sponge is 10,000kg/m^3. This is a rather dense sponge. (Please ignore the plethora of bubbles in the picture...)