June 2006 - Physics

<p>darkruler - no</p>

<p>Maybe it will show I am an imperfect human, not a flawless machine who studies all day. Not that three 800's wouldn't be sweet. ;)</p>

<p>how many wrong would be 700?</p>

<p>The Galileo question shouldn't have been there, it was more of a history question--HOWEVER, if it's counted as a modern physics question then one should be aware that Gamow (and possible variations on the Friedmann models would have) predicted the universe was expanding and Hubble gave expierimental evidence (working independently) in the 1920s. [I believe.] It was based on 20th century technology (Hubble telescope) and the red-shifting of light.</p>

<p>Galileo actually came up with Newton's first two laws of motion and Newton himself wrote the 2nd first in terms of momentum and not F=ma as we write today.</p>

<p>But most of that information comes from A Brief History of Time so, . . .</p>

<p>Now, if only my class covered anything beyond really basic electric changes/forces I could have answered the optics/electromagnetism questions and gotten a decent score. Instead I got a bunch of mechanics/dynamics and modern physics and failed the rest.</p>

<p>Oh well.</p>

<p>Originally I thought this was pretty easy, but now I even think I did better on USH than Physics :(</p>

<p>We need more questions to review.</p>

<p>as for the question with X-Xo=VoT-0.5AT^2, I believe the answer was the case where you had a frictionless inclined plane, because only then was the acceleration constant.</p>

<p>Thin FILM DOES DIFFRACT:</p>

<p>theres a thing called the thin-film effect:</p>

<p>It diffracts visible light thats why theres a thing called negatives ... theres dark spots and light spots ... thats from diffraction of light and interference ...</p>

<p>so is phase shift the answer?</p>

<p>yeah dude thats interference, the diffraction youre thinking of is from slits.</p>

<p>Someone whipped out their textbook and found that there is phase shift, so it can't be that. I still say diffraction; I've never heard of the thin-film effect, but you might be right.</p>

<p>think about it ... when light passes through thin film u get negatives which have differetn variations in color there dark spots and white spots. this is because of diffraction ... look at a film negatives their black and white (bright and dark) which is caused by diffraction which is due to compression and rarefractions of light waves which = DIFFRACTIOn there is no phase change atleast not that i know of and i know what phase change ur talking about</p>

<p>what you guys put for the one about the two balls equal mass but one falls faster </p>

<p>i put buoyancy force cuz it seemed rite but now it doesnt seem so rite anymore</p>

<p>i know its not gravitational or anything to do with mass so kinetic energy </p>

<p>now i think its density cuz look at a balloon, its less than air thats why it rises up ... </p>

<p>and what u put for the one about the bird and GIVE A REASON</p>

<p>i said its gonna be above the surface and but below the bird cuz since its rising up from water, the refracted angle is gonna larger than the incident angle so distance from water to bird image would be closer than distance from water to bird</p>

<p>for the bird one...
the image is above the actual position b/c light travels faster in air than in water so as the image of the bird changes from air to water, the angle is smaller with respect to the normal</p>

<p>Anyone care to count up how many questions we've covered?</p>

<p>Oh man..for the two balls one I put one had a greater surface to area ratio or something..because they have the same density (therefore the same mass) so gravitational potential energy (mgh) can't affect them since they both start off at the same height and fall.</p>

<p>Density is merely the ratio of Mass to Volume, and given the same densities, the object with a larger volume needs more mass to keep the ratio constant. However, the surface area answer was correct I believe. Also, you can note that 2 of the answers were directly about the weight, one listing the gravitational force, and the other expressly saying weight. Knowing that these were infact identical, you can write them both off and make your choice all that much easier.</p>

<p>Yay I got it right!! :D <em>hugs Rizwan</em></p>

<p>But eurgh, I got the fractal one wrong. I put mud, thinking that mud doesn't crack infinitely and that it has no set pattern whilst insect does. Aarghhh.</p>

<p>Btw, for the bird one, I think it was above the surface and below the actual bird since if you have mountain ranges you can see them completely underwater (like if you have mountains surrounding the area and you look up from beneath the water, they all seem to tower there and you can see ALL of them) which means that they are below their actual position..not above. Btw, this was in a textbook of mine where they showed a picture and everything, but it could just have been a different situation. Can anyone confirm this?</p>

<p>just draw a ray diagram. the bird is clearly higher</p>