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.

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.

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.

Fly Gundam!

I was watching an episode of 0080: war in the pocket. I noticed the space colonies were rotating. The different sections had different rotational speeds.

With further research I found out that many of these colonies are called O'Neill cylinders. One the first designs was "island one" a sphere with a diameter of 1.609km (804.5m). So to find the velocity at which the colony would have to rotate is using F= m(vsquared/r) to get 88.8 m/s. Another design calls for a cylinder rotating in different sections at different speeds. There is even an outer ring that rotates at various speeds for farming. In Gundam, the cylinders probably rotate way faster than 88.8 m/s since the rotation is too fast (for visual effect). Interestingly, in Rendezvous with Rama the object being explored also seems to be an O'Neill cylinder except without the mirrors and windows (needed for light).

These cylinders would need to be placed at Lagrange points. These points would allow a colony (only affected by gravity) to remain stationary between two objects, say the moon and earth. <> wikipedia includes some ways to calculate the five Lagrange points. This is demonstrative of center of mass, it being essential. However this is no longer a uniform circular movement since the objects take elliptical paths.

A large problem that confronts space exploration is the effect that radiation in space will have on colonists/explorers. At the scale of the O'Neill cylinder however, the air and the steel (perhaps another metal) hull will be sufficient protection.

Personally I can't wait for space colonies.. there's just something so enticing about space.

Conservation of Momentum

Admittedly this video isn't that cool. By the way, I hope the other embedded video works now.



However, this is an example of (variation upon) newton's cradle. It's better than showing you the one on my desk. Here, momentum is conserved. When one ball is pulled back and allowed to hit the stationary balls the momentum is transfered to the ball on the opposite side and it moves. Here the balls (of same size and mass, and same plane of movement) are involved in an elastic collision. The KE is not changed to anything else. I also see this concept in the bowling ball return. When there is a line of bowling balls and a ball comes back and hits the series of balls only the last ball moves away. So anyways, happy rest of weekend everyone.

Joon Lee!

The other day the car I was ridiing in got hit by another car. Although Hawaii state law is handy with its "no fault" clause it was obviously the other drivers fault. Turning onto a one lane street and signalling, the other driver (Joon Lee) sped up to pass and crashed into the front right of the car.

Now the car door hardly opens, however, I feel pity for the other car which seemed to sustain even more cosmetic damage. Fortunately nobody was hurt although my neck felt a little stiff.
I feel what helped reduce the effects of the minor collision were the "crumple zones" on the car. Although the impulse of the collision is the same, it increased the duration it took the other car to have the collision and thus reduced the average force. Thank goodness for that. Happy rest of weekend everyone!

Rube Goldberg FTW!

I'll have to say that Rube Goldberg contraptions are awesome.

In what is basically an interactive physics program, Garry's Mod, one can simulate different physics (gravity, even static and kinetic friction) but heck, to put it bluntly, nobody talks about Gmod in those terms very often. But! when you're messing around with Rube Goldberg contraptions very minute differences can make something go amiss.

So here's a video that I really like. Everywhere there are examples of physics. I like the part at the end where the crates slide down a massive ramp. The people at the end are encountered by a massive load of kinetic energy because satrting from higher up means more potential energy and we all know for conservation PE + KE = KE +PE, although I wonder if the creator had to reduce some friction on the ramp. Well anyways, this is some fun fun stuff (to me at least :p). The only limit is imagination! (ha what a hackneyed phrase)