Physics

I came across this while reading--If an object approaches/moves away from a mirror with velocity v then the image approaches/moves away from the mirror with velocity 2v. Isn't this wrong? The image should approach/move away from object with 2v rather than from mirror. Thanks.

Ultrasound lasers (sasers?) work because the frequency is high enough to keep sound from spreading out much. I was wondering what would happen if two sasers were pointed at the same spot on a rough but non-absorbing surface? Could the interference patterns of two ultrasonic waves create audible sound from a distance?

So I'm trying to picture a scenario here. (Not a homework scenario, just a hypothetical I thought of years ago that came back to mind recently.) A bunch of people need to be rescued from a fire, but there isn't enough room in the helicopter, and the only thing attached to the helicopter they can grab onto is a spring. As they all leap onto the spring, the helicopter begins oscillating vertically; as in, they rise when the helicopter falls, the helicopter rises when they fall, etc. Presuming they didn't otherwise exceed the helicopter's weight load limit, would the vertical motion prevent the helicopter from achieving the kind of lift it would need to achieve i…

Now when the spring recoils, it loses its elastic potential energy to the dart. If it loses its energy how does it come back to its original shape. I'm thinking it is the elastic potential energy that is used to make the coil come back to its orginal shape. Also let's say a spring was compressed and I took my hand away. Now it recoiled back to its shape. The spring didn't transfer any of its added elastic potential energy, to any other object. So does the spring has more energy now. When I compress a spring I'm thinking I'm adding extra potential energy. Am I adding extra energy or, changing the allready existing energy in the spring to elastic potential energy. …

Hello everyone, When you go down a lift, are you actually falling down. Is the lift carrying you down, or are you falling down due to gravity towards the lift, if the lift goes too fast would your head crash? Sorry if my thinking is completely wrong. Ok now apparent weight is from the normal reaction force. Muscles pump blood up via veins and then they fall due to gravity and other factors. So when they fall and hit the interior of the foot, can't you feel it. So isn't apparent not just the normal reaction force. Thank you

Don't sure this is the right forum for my thread because I am referring about a medical device that is blood analyser. The problem of this device is it can't suck the blood sample in the pre-dilute mode. The blood will be attracted into a so-called White blood cell basin. At that time, a plastic pot is at "negative pressure" and it connects to White blood cell basin via a valve. In the others way, the tube that sample will be attracted into also connect to that basin. So when I test "ON" that valve while no using sample (means the tube is connected to air pressure. The basin get two pressure, "-" from the pot and "+" from air. And so in that test mode, another motor …

How many of the 700 or so numbered VFP errors can you successfully recover from programmatically, and allow execution to continue?

Hello i'm new to this forum and i'm facing some problems while dealing with this question. A particle is moving along the x axis in SHM. It starts from the equilibrium position and moves towards the right at t = 0 s. The amplitude of the motion is 2 cm, and the frequency is 1.5 Hz. 1)The equation for velocity can be determined by differentiating the function for displacement w.r.t. t, V = AWn cos (Wn t) Therefore, the maximum speed will be |V max| = A(Wn)(1) <---- what is this? where does the (1) come from? 2)The time that it first occurs could be found as follow; cos(Wnt) = −1, <--- why is it -1? Wt = cos−1(−1), t = 0.33 s.

Hi all, Im new to SFN so sorry if this has been discussed, just wanted to know if there was anyone out there who could explain to me how vibrations from sound can be converted to electricity, though Im sure it is possible I cant seem to get my head round it. Thanks in advance.

http://www.youtube.com/watch?v=HzfUDHa0RJo http://www.youtube.com/watch?v=Wl4mUCYKyz4 I just thought these would be cool vids to share for my first post. Does anyone have any better vids of possible black holes? These vids have amazed me since I first saw them a few years ago on a doco on, well, Black Holes amazingly enough.

Is it totally true, that when Newton's second law (f=ma) is violated, a heavier object when pushed would accelerate at the same rate as a lighter object with the same force? Now don't get me wrong, I do know that physical laws cannot be violated.

What I learned in physics about visible light is that the shorter the wavelength the more energy it has, thus red which has the longest wavelength is the outermost color on the rainbow because it bends the least, colors with longer wavelengths bend less and also have less energy. Likewise, violet has the shortest wavelength and that's why its the innermost color on the rainbow, because it bends the most with its short wavelength. Also since it has the shortest wavelength it has the most energy so therefore violet lasers are the most powerful. So this being the case I would like to say that Samuel Jackson is smart. Samuel Jackson who played Mace Windu wanted a purple…

A group of violins playing unison the same note on an orchestra... The particular vibrating string emitting the sound cannot be perfectly synchronized from one instrument to another and another. Why there is no perception of tone nodes/antinodes constructive/destructive interference/interaction, but a smooth equal pleasant sound ? When the string is moving 'upwards' in instrument 1, the string in instrument 2 can be moving downwards. Plus any tiny-tiny deviation in tuning the instruments should create noticeable interference. Or the distance from the ear to one or another instrument... Reinforcement or cancellation is not perceived. It sounds just as a maje…

do they violate causality since they travel faster than light and violate conservation?

When I was a teen and our San Joaquin valley had supper sonic jets over our valley that rattled windows with sonic boombs. Shock waves can be seen visually. There was a supper sonic jet over head with a thin cloud layer and about 3/4 mile behind there I saw a large shock wave following. The shock waves travel in straight lines one after another.

Why does the hydrogen (3,2,1) wavefunction look so similar to the field lines generated on this CRT?

Introduction I think most of you are familiar with Newton Issac and Albert Einstein's gravity theory which seem to involving gravitational relationship between objects, whereas this I approach is singular (focus on an object or object's gravitational individuality as possibly fundamental which relation / relativity (e.g. general relativity theory) happen possibly because of it. Diagram A diagram of the gravity equation formulation developed by myself as part of self-learning with the gravity within both classical physics and quantum physics although is singular for time being, supposedly applies to an individual object - but not yet approach relation / relativity (e.g. ge…

What's the scientific word for this? Like... not comparable in a sense.

I need to understand the relation between volt (V) and electronvolt (eV) in a system with particle and electric field. Let say that we have 2 larges plates in a vacuum and two test charged particle a proton and an electron. The distance between the plates is 1 meter. The electric potential between the plates is 100 volt and the charge of the particles are +1 and -1 elementary charge. If the plate are large enought the electric field gradian is constant in the middle betwen the plate. An electron at the negative plate will experience a force toward positive plate. I am tempted to tell that the electron will have an energy of 100 eV when it hit the positive plate. Is…

Hi everyone, I'd be really appreciative if someone could clarify a few things for me. 1) If voltage is the potential difference, surely the 'difference' necessitates at least 2 different values, so there is something to differ. So, is the voltage the potential difference from one end of a circuit to the other? 2) Is the energy actually from the voltage? Or is it caused (transfered) when the voltage causes the charge to move through the circuit? thanks

Hello guys, I'm struggling with these type of circuits. Here is my question. I have drawn a diagram in paint When the input AC voltage= 0 v the collector current is found to be 1.0 mA. The current gain of the amplifier is 200. There must be 0.7 V between B and E before current can flow from the collector to the emmiter. What is the resistance of Rb Well I know that Ai= Ic\Ib and I can find Ib but I don't know how to use this information. My understanding of series and parallel circuits is good but I don't know how this type of circuit works. If anyone can give me a detailed step by step of how this system works I'll be reallly really greatful

Hmm Ive been wrestling with this for a while now (hence my return to sfn ). It goes as follows; Imagine a wire of 0 resistance. OK so unless there's a rule of physics im missing then we arn't loosing any energy in the wire. So i decided to wave a flornscent tube around the wire. The magnetic fields around it make it glow. . So wheres the energy coming from? By introducing the florescent tube am i introducing a voltage drop?

The ionization energy of H is 13.6 eV With that information how can I estimate the volage I need to apply to 2 electrode in a H gas in order to get H+ ions ? What is happening to the electrons ? Can I get 100% of the H atom ionized? Thanks

When I connect two 1.5 V batteries in series, I get a potential difference of 3 V across the terminals. |+|---- |1| | |-| | | 3 V |+| | |2| | |-|---- (Showing battery 1 and 2 in series). Can anyone explain why the voltage is doubled when voltage sources are connected in series? Why, for instance, is current not flowing from + of battery 2 to - of battery 1 (conventional current flow)?

This is a response to an emerging discussion in another thread about the common claim that most of an atom consists of empty space. My question is whether it makes sense to attribute any volume at all to the constituent point-particles or if that's like claiming that 0-dimensional points make up a small amount of volume in a 3D object. Can electrons, protons, and neutrons be described as having volume and "empty space" or do they generate volume/space with their energetic interactions: from previous thread: Ok, but nuclei are configurations of particles, not particles themselves, right? I'm just wondering if there's any basis to that assumption that the partic…