Classical Physics

1) If you had a lightyear-long pole made of some sort of exotic, super-strong material that would not bend under any circumstances, would it be impossible to move due to the fact that the far end would have to react faster than the amount of time it would take for the information from you to reach it? 2)Would a voluminous material strong enough to hold its shape perfectly be impossible, or would it be impossible to move? 3)Would something strong enough to hold its shape perfectly have to be infinate in density? 4.1)Singularities can move. Is this because they are infinately small in volume? 4.2)Something with volume and infinate density would be infinate in m…

Hey guys! Nice forum! Here's my first question. How do we get this expression for the velocity: [math]\dot\vec{r}=\dot{r}+\frac{l^2}{m^2r^2}[/math], where l is the angular impulse of force I thought we could do it like this: [math]{\vec{l}}^2=l^2=(\vec{r}\times{{m\dot\vec{r}}})^2=m^2{}r^2{\dot{\vec{r}}}^2-(\vec{r}\bullet{m\dot{\vec{r}}})^2[/math] We can't simply write:[math]{\dot\vec{r}}^2={\dot{r}}^2[/math], since then l=0. But why? Which rule forbids that equality. Similarly we can't treat the scalar product above as we would wish to. So how should one proceed in this case? Thanks

I've been browsing the internet and have found sites where you can actually buy Uranium metal. Now I don't know if you need a specific kind, 235 or 238, but the basic ingredients in a fission bomb are Uranium and a case of TNT to implode around the Uranium. I'm sure there's a lot more to it, but what? Is 238 what they call enriched Uranium? Is this what's required? Just kinda confuses me if that's all there is to it. Thanks.

Let's say we have [math]m[/math] kg of oxygen at [math]T_1[/math] K. After heating the oxygen, it did [math]A[/math] J of work. Find the temperature to which the oxygen was heated. [math]p=const[/math]. This is all simple of course, using the [math]A=p(V_2-V_1)=\frac{m}{M}R(T_2-T_1)[/math] formula. Now we are able to find how much did [math]U[/math] change using the [math]U=\frac{3m}{2M}R(T_2-T_1)[/math] formula. Since [math]Q=U+A[/math] according to the first law of thermodynamics, [math]Q=\frac{5m}{2M}R(T_2-T_1)[/math]. Here's the problem: [math]Q=cm(T_2-T_1)=\frac{5m}{2M}R(T_2-T_1)[/math] from witch [math]c=\frac{5R}{2M}[/math]. Numbers don't show that the given f…

Hi. A toy car receives the impact of a horizontally going projectile onto its solid, metallic, vertical rear bumper, and the projectile bounces back. The same toy, weighing the same as before with a springy or rubber bumper, receives the same projectile and it does not bounce backwards at all, just drops vertically after impact. Which case will push the car more distance because of the impact ? Miguel

If an object did not have inertia, and a centripetal force acts on it, how fast would it go and what radius would it turn in? Also, could the object turn in the beginning/middle of a turn without slowing down? Also, can something without inertia turn while in the middle of changing direction and do the same thing many times?

As far as I understand it, the only thing that allows man to observe the world around him is by way of this little invention called "the lens". If it wasn't for this lens to focus photons coming from the same point on the retina than the eye would just get bombarded by a huge load of photons with no idea of where these came from and no means of building up a coherent picture. Am I the only one that finds this mind boggling that nature come up with this neat device that allows us to make sense of the world? And if you follow through on this then we are damned lucky that light changes direction when passing from one medium to another. How would you else go about ma…

Hi guys! I am pretty sure I am going to regret it, but I'll ask anyway! Let's say, you have two magnetics. One is an NIB (rare earth magnet, really powerful) and one is a fridge magnet (vey weak). Now, you also have a fixed lenth of wire connected to an ammeter/voltmeter. If you run each of the magnets down the wire, at the same speed, the rare earth magnet produces a greater current, we all know that. Consider this: Your kinetic energy is being changed by the magnetic field into kinetic energy. This means that the NIB magnet is has a greater efficiency. Please correct me if I am wrong in any of the statements above, but, what exactly is going on …

My teacher told me that there is no effects on the gravitational acceleration from the horizontal motion.... For eg, if we throw a ball horizonally in the same height as we drop the ball, both should reach the ground at the same time.... but I and my mate did an experiment. We put a trolley on a slope of a certain angle, although the trolley has constant acceleration, but it is alot different than the gravitational acceleration!! Any body can explain the principle behind it?? Albert

Hey there, Quick question, any ideas on how to solve would be greatly appreciated. Q: At a distance 'H' above the surface of a planet, the true weight of a remote probe is one percent less than its true weight on the surface. Find the ratio H/R. Thanks all. Kev

I think this goes under classical mechanics (it's classical physics anyway). Suppose I had a cooky try with 1/4 inch deep water in it. If I let it sit on the kitchen counter, would it eventually evaporate? If it would, how long would it take? If it wouldn't, what conditions, in addition to those listed below, would be needed? My house is a little above room temperature (25 degrees celcius). I live in Calgary, Alberta, Canada which is at an altitude of about 1 KM above sea level (and I live 5 stories up). It's the spring season with temperatures around +20 celcius (on good days). What if I left it out on the balcony on an average day (~20 celcius with mild wi…

last night one of my friends gave me this question. if a helicopter were to fly up in the air and stay there hovering fo a few days. when it landed why wouldnt it be on the other side of the earth? i did answer, i said that with the earth as the frame of reference and within the atmosphere. the helicopter is considered motionless when it is moving with the earth at the same speed as the earths rotation and orbit. and that for the helicopter to move it requires velocity or at least a speed greater or lower than motionlessness. which while it is stationary it doesnt have. im not sure if my explanation was right or not. what does everyone think? could you give …

Ok, so I was at a bar last night where, on the tables, there were little "lamps" that consisted of a plastic jar of oil with a cloth wick and flame, inside a glass vase. I noticed that when I tapped the table anywhere, the flame would flare for a split second (so quick its not even noticable unless you're paying attention), practically doubling in size. It wasn't a gust of air, since waving my hand at it, changing the place where I tap the table, or taking the jar out of the vase had not effect. I tried the same thing with a butane lighter and a propped up match, and nothing happened in either case. This leads me to believe that it had something to do with the wick, but I…

I found my car this morning blanketed by frost. After cleaning it, I started driving and thought if heat is a source of energy, what is “COLD”? is it negative enerty?

This would be purely for fun, but what is the equation for a large volume of low density gas effecting the gravitationl pull of a higher density object, if the two are attached. My housemate wondered if you could manufacture a helium suit...and quite literally float around, roughly a foot off the ground. As long as the helium volume is proportianal to the mass it's carrying, surely you could work out how to make the suit float at a regular distance from the ground, by applying earths mass. The shape of the suit maybe odd to attain lift, but a suit all the same.

A red snooker ball of mass m and radius a is at rest on the snooker table. The white ball's centre is travelling along a line that is tangent to the red ball. The white ball also has a mass m and radius a. The coeffcient of restitution for collisions between the two balls is e. (a) Show that the speed of the red ball after collision is (square-root 3)/4 * (1 + e) times the speed of the white ball before the collision. (b) Find the angle that the white ball's path is deflected by. © Show that no energy is lost in the collision if e = 1. Does anyone have any hints on how to solve this or know how to solve this thankz

First of all i wasn't sure where to put this post so if it needs to be moved or reposted elsewhere please let me know and i will do so. So heres a quick background, i'm a senior in highschool and at my school it's tradition to ask the girl you want to go to prom with in a very creative way. I had some friends write "Will you go to prom with me?" in huge letters in the girls street, others had streakers at a football game with "Ally prom with me?" written on their butts, and other creative ways, some romantic, some not so much (is male frontal nudity a good way to ask a girl?). Anyways here is my idea... I want to go to the creek like we always do and have a sm…

Does anyone know how to solve this please, don't even know were to begin with this problem. A spacecraft and its cargo (a satellite) is circling the Earth at a constant speed and an altitude of 600km. Their combined mass is 1.20x10^5kg. At thi = 0, the captain ejects the 1.10 x 10^4kg satellite out the back. The speed of the satellite relative to the spacecraft at the time of the separation is 100m/s When the spacecraft reaches thi = pi, what will its altitude above the Earth be? Thanks

What will the reading be if I pass ultrasonic wave towards a metal wall, where I put a CRO beside the transmitter? A linear equation with a negative slope or y=k with several crests?

How are rechargable battery recharged again? Which physical quantities should I consider to estimate the time needed to make the battery full again? The electricity capacity (ampere-hour) or the energy delivered to the battery.

This is a qusetion about pressure and diffusibility. If i apply pressure on a shoe having a provision for inlet of air like in a nike air shoe only with hole spaces for air inlet(wearing it)and then relieve the pressure by lifting up my foot will the air from out side move in? And if so will it have enough energy(if narrowed space is provided lining the upward direction)to move up and will the air be cold or warm as it moves upward if its initial temp is room temp?Also suggest a way by which the temp can be practically significantly(20* or so)reduced. I am sorry if it aint clear enough coz i am inexperienced in physics ie. 7th grade:confused:

How does moment of inertia apply to all the martial arts kicks, punches and other moves?

I am trying to apply the laws of physics to contortion acts (backbend, splits, etc.) However, I do nkt know what laws of physics apply to the contortionist's flexibility. Could someone please help me out? Also, I mean physics when I say it so I do not a reply saying this should do with biology.

Given data: 250Nm @ 1900 tr/min. (TDI 1.9L engine, VW Jetta 2006) 0-80 km/h (0-22.2m/s) in 8,0 sec Car weight: 1384Kg (empty) adding a person and fuel lets say 1500kg We can assume that the car speed is rising more or less linear between 0 and 80km/h. That is even logical if an automatic gear is trying to keep the tr/min around 1900tr/min resulting in a constant torque generated by the engine. The calculation: The average acceleration of the car is measured at 22.2 / 8 = 2.8 m/s² The needed average force to get this acceleration is 1500kg*2.8m/s² = 4200Newton (m*a=F) The torque is 4200N*r=250Nm --> r = 0.06meter (6cm) So what went wrong what…

Hi guys, well if you can't tell from the thread name, ill explain what this is all about. I am studying year 12 physics in victoria, as one of my sacs (Student assessed course work) i need to do an EPI (extended personal investiagtion) on the topic of motion. What this thread is about was if anybody out there with a physics mind would be able to help me with an idea of what to do, you see because i appear to be in abit of trouble. The prac work has to be done this comming Sat 25th of feb, i know i have left it late, but i thought by now i'd have a good prac to do. I was wrong, so i need abit of help. Now a little information on the actual prac, i have 4 hours to d…