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Also, a funny pic

Rejoice! For Kim Jung Ill is finally dead!

http://www.youtube.com/watch?v=CceXXXubvdE

I found this picture to be relevant to our topic....

I found this to be really cool and relevant to the buoyancy topic.

Every year, there is a race in which participants race with canoe. But, the canoe is not your everyday canoe. In this race, you need to race with canoes made entirely out of concrete.

To do this, the participants must carefully design their canoe through complicated calculations and provide enough buoyancy to float the canoe and the racers.

For more info, check out http://www.asce.org/concretecanoe/

So I submitted my lab Yesterday at 10 p.m.

But I did not realize that it is first saved as a draft.

I revisited the site a bit after 12 p.m. only to realize my work was not submitted.

I then proceeded to click the "Submit" button frantically hoping that time will some how bend.

So... Am I late now? I sure hope not....

One problem we encountered in the recent Experiment

Weight, why you no stop swinging

Llittle thing I found in the glorious Internet

Today, Mr Love surprised us with his use of amazing science/magic. Although our class didn't have the opportunity to discuss the reason for such amazing displays, it definately involves angular momentum.

I my opinion, the reason why objects behaved such a way was because they were trying to preserve their angular momentum. To cope with the change in position, it exerted the force in different directions.

Conservation of Angular Momentum

Have you ever seen an ice skater and wonder why she spins slow with her arms out but spins fast with her arms folded?

This is due to the Conservation of Angular Momentum. Unlike normal momentum, this involves only shape and velocity.

Therefore, when the skater folds her arm, she has to speed up to compensate for the loss of shape.

Funny Physics Joke (semi true)

A physics professor, who was teaching a graduate course on superstring theory, decided to add an essay question to this year's final exam. The instructions read, "Describe the universe in 400 words or less and give three examples.

They say that triangle is the strongest shape. Why? Because force in one point is distributed to numerous points in the base.

It is no surprise that triangles are used in many structures these days

Why do bullets cause so much damage? How does a small piece of lead do such horrible damage? According to the physics, its because of the way bullet is shaped.

The tip of the bullet is lighter than its rear and when it enters the flesh, it loses its spin. As this happens, the bullet becomes unstable and the heavier rear gets ahead of the tip and the bullet tumbles. This causes a large internal wound which are deadly.

We learned about the cemter of mass today and that got me thinking... Does center of mass has to do something with the movement of boomerangs? I'm not sure I would appreciate somebody explaining it to me

Another Cool thing I found in Internet

We know from The Virtuosi's work that the recoil impulse is about 4.5e-7 kg m/s. Let's say the laser gun has a mass of 5 kilograms. Dividing the impulse by the mass of the gun gives a recoil velocity of 9e-8 m/s. Since kinetic energy is equal to:

We have a recoil energy of about 2e-14 J. This is pretty tiny, but then again human ears if not human skin can detect some pretty tiny sound energies. Now in a context like this the pressure of a sound wave is given by

Where I is the intensity in watts per square meter and v is the speed of sound in our material. We don't know what the intensity is, but we can estimate it by saying that it's equal to the energy (2e-14 J) divided by the time of recoil (probably milliseconds, not micro/nanoseconds because of the difficulty of propagating very short acoustic pulses in bulk media - let's say 1ms to be generous), divided by the area of the shoulder stock (say, 25 cm^2). Taking the speed of sound in the shoulder stock to be the 3300 m/s value typical of wood gives us a sound pressure level of about 2.4e-12 pascals. The threshold of hearing is about 20 micropascals, which is much higher. Even assuming the sound pulse really is only 1ns long doesn't quire reach the threshold of hearing. If the pulse couldn't even be heard it probably can't be felt.

Few cool points I found about the way wings work.

The amount of air diverted by the wing is proportional to the speed of the wing and the air density.

The vertical velocity of the diverted air is proportional to the speed of the wing and the angle of attack.

The lift is proportional to the amount of air diverted times the vertical velocity of the air.

The power needed for lift is proportional to the lift times the vertical velocity of the air.

Size Matters!

Why is it that sniper rifles have longer barrels than other guns? This is because when the barrel is longer, the power of the charge is pushing the bullet longer which, in turn, equals to more powerful bullet.

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