Classical Physics

Once again, we have a trick question, based upon mixing elements of different Electromagnetic theories, i.e., classical and modern. In classical electrostatics we would apply the Sphere Theorem and simply declare there is no radiation outside the sphere, since the potential field does not change. A sphere of any size acts as if the charge were concentrated at the centre, and if the centre does not move, the field does not change. Likewise, the field inside the sphere does not change, since it remains zero at all times everywhere. The only place the field actually changes is in the region between the smallest and largest diameter of the pulsing sphere. This…

hey i am not sure whether i am getting this problem correct... i reckon the answer would be: f(n) = nv/{lamda1} ; where n = 1, 3, 5, 7, . . . {lamda1} being the fundamental harmonic's wavelength, and v being the speed of sound in air well anyway, thats what i think the answer is but yeah i am new to thise stuff, so just thought i'd check -Sarah

First, let me state that my physics was below average when I studied it and it's been years since. And not just a few. Also, I did it in a different language. So. I have a few questions about a debate I started with a few people about a car's stability and I'm kinda stuck. First, is a lighter car harder or easier to tip over? I know center of gravity is a big factor, but is it the only one? I mean, if a 600Kg vehicle and a 1 ton vehicle have the same wheel span and the same center of gravity, shouldn't the heavier car tip over at a higher speed? On the other hand, the lighter car generates less friction so it is more likely to skid rather than tip over. Both main …

hey i am not sure if i have done this problem right.... as i have not used either of the bits of given information about p = 1 and at what lengths the resonance occurs at :S well anyway, heres my answer, what do you think?

As the phrasing indicates, the 'bisector' is only an approximation of the direction of the force from a charged rod or string of mass-particles. Let's see why: Lets look at the proposal of the question in a diagram: Now lets look at a simple theorem about circles: Now lets choose a test-point which is on the rim of the circle of unit radius around the geometric centre (midpoint) of the rod. This will make the directions from our test-point to each end of the rod a right-angle. First lets take the most simple case, of two equally spaced like-charges on a rod, or else a string made of two Hydrogen atoms (a diatomic molecule of H gas): Th…

Can anybody tell me how strong our hand can tighten a screw(in Pascal)? Thank you very much and sorry for my English

hi i have a rather simple question if i have a bunch of balls lined up so they're touching each other, and i throw a ball on one end of the chain, the ball on the other side of the chain will pop out take a look at this guy's avatar, err, he has nothing to do with me, im just using his avatar cos i dont know what those desk gizmos are called http://www.scienceforums.net/forums/member.php?u=5728 now is the energy transfered from one ball to the one on the far end instantaneous? if so, i thought nothing could travel faster than the speed of light doesnt that mean that if i had a rather long rod, i could poke a message to someone that was quite far away, eg…

Just had an idea about this and i can't find any threads about it either. Orbital velocities are slower than escape velocities, so you could theoretically orbit a blackhole inside the event horizon(assume its so massive that there isn't a whole lot of sheer) without breaking any laws of physics(i think). To escape you could change your apoapsis till it is above the event horizon and still be going below c. when you get out side the event horizon you just bring your periapsis out of the event horizon by accelerating again and you could then accelerate to the escape velocity at that altitude. any flaws here?

If a magnet is brought near a rotating copper disc, the disc will slow down. This is because of the electromagnetic drag force. Does the same thing happens to a rotating superconductor disc?

You have 2 objects of mass (M and m). Object M is used as the frame of reference so has a velocity of 0, however object m has an initial velocity of "u". The distance between them when t=0 is d. Object m is heading straight for the centre of M. Now ignoring gravity that is a simple problem (working out time till impact, t). However the reason why I don't know how to solve it is that I would like to include the effect of gravity between the objects. So I would like an equation that gives time until impact assuming that both objects are point objects and all other gravity can be ignored. I'm assuming calculus will be used. Thanks.

If a magnet is brought near a rotating copper disc, the disc will slow down. This is because of the electromagnetic drag force. Does the same thing happens to a rotating superconductor disc?

An egg is placed between 2 boxes of mass m and M (M > m). The 3 objects are in a straight line on a table top. Scenario 1: A force is applied on the larger mass until the whole system starts to move. Scenario 2: A force is applied on the smaller mass until the whole system starts to move. Which scenario will the egg be more likely break? Explain. Assume that the egg and table have negligible friction but the friction on the 2 boxes are not negligible. Friction, Fr >= kN, where k is the coefficient of static friction and N the normal contact force with the table top.

Well, for my assignmetn we have a parachute, our testing hasnt been thorough enough to determine fully the effects of our three variables , which are: change in surface area differnet shaped parachute with same surface area addition of weights to the parachute base Well the change in surface area is alright, but the different shapes we have, a rectangle, circle and triangle. aafter testing them the time they took to be dropped from 2 stories high, they all took around about 7-8 secs long, but it was a bit windy and results are not very accurate, we didnt have long either in class to do it. What im asking is, 2 things, should the three shapes show different r…

I work at the park teaching little kids to swim, play tennis, etc. In the pool, I have them floating on their backs for example. Two same size kids. Holding there breaths, one floats easily but the other struggles. No matter how much air he takes in he has a tough time. Why? Bettina

A mechanical device is something that takes energy input, modifies it, then outputs it in such a way that it assists in the performance of a task. A lens takes light input, modifies its vector, then outputs it in such a way that assists the performance of the eye. So is a lens a mechanical device? I think so, but I'm having a hard time convincing a friend that glasses are mechanical devices. He keeps saying it must have moving parts to be a mechanical device.

Yes. Since the Centre of Mass 'method' and Sphere Theorem are only approximations, they also implicitly predict gravitational waves. Therefore the existance of GW is not a strong proof for General Relativity. Comments? Next he'll say Newtonian gravity bends light too!

Can anyone show me a proof of "refractive index= (real depth)\(apparent depth) "? I found the proof in my book has a mistakes and I found some contradicts to this equation. The book said used a pair of similar triangles to infer it but the triangles are not similar. Hope it helps you bring me out of the troubles.

how do photogates work?

hey dudes i hope its not too much trouble but i have a few questions that i don't know how to answer and was wondering if anyone could help; Draw graphs to show relationship between: a) FORCE and ACCELERATION for an object in circular motion b) MASS and DISTANCE for forces due to gravitation c) The PERIOD of orbit of a satellite and its ALTITUDE hope its not too much trouble, thankz for ur help Lil' Pac

Hello I've no grounding whatsoever in physics but am trying to workout a magnetic strengh problem for my own amusement. I've spent several hours reviewing physics web sites but am totally confused. How do I go about modeling the following situation? I have to permanent bar magnets on end. Both are held vertically within a tighly fitting tube so that they cannot move sideways. The tube is sealed at one end and open at the other. The magnets have their like poles pointed at one another so that they repel each other and (assuming their strong enough) one floats above the other. If I begin adding weight (something non-ferrometalic) to the floating magnet the air gap …

one of my quations looks weird. And I found out that it's because that at certain conditions the gas is travelling at nearly the speed of sound but I can't really figure out why. is it because that for the gas to break the sound barrier, it needs to liquefy. but there's too much energy, so it can't?..or is it...well I don't know...and my head hurts. so why can't gas travel faster then the speed of sound? 'have it nicely'

(I think this is the right place to put this) Ok, so i have a TV in my room, and whenever its on and i put my hand or something near it, you can hear static electricity. So, sometimes i put the TV on to play some games, and i have a Portable CD Player in my hand. Then i put the CD player on top of the tv, and the earphone wire hangs down, getting close/touching the screen - i can usually hear the static when it does that. This time though, i did the same thing, but the static was louder, and my CD Player turned off. I never learned Electricity in physics So i was wondering, how was there enough from the TV to turn off the CD player? First time its ever ha…

A man holds up a 100 pound weight. He applies a force to the weight of 98 Newtons to hold up the weight (f=m*a). Gravity likewise applies the same force. However, the man will eventually get tired, but gravity will not. Gravity's force is eternal. Doesn't this violate conservation of energy? The same is true of the other 3 fundamental forces.

Hi all, im doing a physics experiment on soda bomb cars.. for those who dont know its a soda bulb placed in the back of a wooden small car,.. it travels around 20 metres in 1-2 seconds.. For our physics experiment, we have CHOSEN to do this and we have to like.. talk about different effects on the car, one is how weight affects it.. ie, adding different weights on to the car and checking how this affects the time, deceleration, initial vel and final vel, etc. Now, we need at least 3 things to talk about, another could be different surfaces, or different inclines... but the one i need help with is aerodynamics. We could attach differnt shaped things onto the car t…

There are so many of you willing to answer a layman's question that I hope you don't mind a few more. With my bicycle upside down(changing tire) I spin a wheel. The spokes appear to curve. I assume this is because the outer end of the spoke is travelling at a higher rate of speed than the inner portion. If I were to accelerate the rim to .999999c would the spoke curvatures be so great that the distance between the rim and the wheels hub appear to my eyes as to be close to zero? Could I asume that the apparent curvature of the spokes are now extremely exaggerated to the point where they appear to be flattening out? In other words the rim is closer to the hub. Eve…