Sunday, November 25, 2007

Bungee Jumping!

So that's a short on bungee jumping at the original bungee jumping site in Queenstown, New Zealand with an introduction by a bungee company.

If the spring action on the bungee cord wasn't dampened then this would be an example of simple harmonic motion. However, no one would be able to stop, so that wouldn't be good for advertising. The motion is periodic, as it repeats itself with intervals in a specific manner; it is described as being sinusoidal, with constant amplitude. A motion with frequency f has period = 1/f. Thus if there was a period of 4 seconds the frequency would be 0.25 hertz.

Okay well that's it from me. I'm going to enjoy the rest of my thanksgiving break. There really is so much I have to be thankful for and I should be thankful year round.

Monday, November 19, 2007

The Challenger Deep

My homepage for Safari is a random page on wikipedia. I'll say that 40% I find a useless irrelevant page like one on some unknown district in India or in Minnesota. However, the other times I can find true gems and oddities (Vang Stone or Australian Senate election of 1967). This time though I found something that correlates with my work in physics and fluid motion.

The Mariana Trench is the worlds deepest oceanic trench. It goes down to a maximum 11 km down. This makes it the deepest location on the surface of the earth's crust. It is located where the Pacific plate is subducted beneath the Philippine plate. In 1960 the bathyscape(similar to a spherical shape so as not to be crushed by the intense pressure) "Trieste" reached the bottom with two men. The gauge presure of the seawater at the bottom is 1030kg/mcubed times 9.8m/s squared times 11000m. This is equal to 111034000 Pascals. This is over a thousand times greater than the atmospheric pressure we experience at sea level! It is almost scary to imagine the sheer darkness and fear one would experince being at that depth, although life persists even at that depth (foot long flounders and shrimp).

So now I've gone from space to the depths of the ocean. Hauntingly but beautifully, physics is omnipresent.

Saturday, November 10, 2007

Eleven Flights More :(

Mission STS-120 was a space shuttle mission (Discovery) to the ISS that was launched on October 23 and landed this Wednesday the 7th. Sadly however, I was reminded that only eleven more missions will be flown by the space shuttle program until its decommissioning in 2010. On a better note the ISS is one more module closer to completion as the Harmony module (a US module built in Italy as part of a joint ESA-NASA deal) was attached; it is a habitat module, and repairs were also performed.

The ecape velocity needed was 11200 m/s this escape velocity does not depend on the mass of the space shuttle although it may require more or less energy depending on the payload of the space shuttle. The space shuttle escaped earth gravity to enter into a LEO or low earth orbit to meet with the ISS at about 320 km above the earths surface. The value of g at this height is GM over (r + 320km)squared. However, since this is at such a low (comparatively) orbit the value of g here is nearly the same as on the surface. The weightlessness is caused by the effects of freefall.

Sunday, November 4, 2007

Heres a video that made me wonder what the initial angular acceleration of the system with the Tundra truck would be if my family's four door sedan was placed on the other side of the seesaw. Assuming the whole seesaw is 70m long then the Tundra truck would be at 25m from the fulcrum while on the otherside my family car would be 35m away from the fulcrum on the right side of the seesaw. The video states the truck is 10000 pounds (4535.9 kg) while my car is probably around 4000 pounds (1814.3 kg) and the mass of the seesaw is probably 10000 pounds (4535.9 kg).

First, inertia of the system would be needed. I = (truck)mr^2 + (car)mr^2 + IS
By substituting values for the variables and I of the seesaw is 1/2ML^2 one finds that the system's moment of inertia is equal to 6909614.2 kg*m^2.

Now net torque is found by adding the torques of the car and the truck. Which is 488990 N*m.

Σt = iα and so angular acceleration is 0.0708 rad/s^squared. Its kinda slow but it makes sense when dealing with large masses that are nearly equidistance from the fulcrum.

In the video it is clear the initial angular acceleration is much larger when only the truck is on the seesaw at a great distance from the fulcrum.