# Search results for query: *

1. ### I Why can't objects be seen if the wavelength is too long?

This is great, I am really liking this one. Guess I should have started with diffraction first :)
2. ### I Why can't objects be seen if the wavelength is too long?

I have read that article yesterday, but it still uses a water/physical peaks and valleys analogy. Is there really no satisfying classical explanation?
3. ### I Why can't objects be seen if the wavelength is too long?

Well in general, the relationship of visualizing/detecting small things with too long a wavelength. Like trying to see an atom with visible light.
4. ### I Why can't objects be seen if the wavelength is too long?

Sorry, this has been asked a few times, but nothing's getting through to me. I really need to satisfy this curiosity :( I've read a lot of "water wave" analogies, but they don't make sense. A water wave has physical peaks and valleys, and I can see how when the peak travels and hits a ship, the...
5. ### Conservation of Energy on Current-Carrying Wire in Magnetic Field

So force on a current carrying wire = ILxB. If I have a bunch of bar magnets making a uniform magnetic field of strength B, then a 1 meter long wire of 0 ohms carrying 1 Amp, the force on that wire is (1)(1)xB = 1B. If I let that force move the wire for a time T, let's assume the wire moved a...
6. ### How does the saturation flux density affect magnetic field strength?

So I'm confused what the Saturation Flux Density is referring to. Defintion says it is when you no longer get an increase in H-field when increasing external B-field. So, does the satuation flux mean the core can only create fields UP TO that saturation flux, or that it can make a stronger...
7. ### Understanding energy conservation in a solenoid

Thanks, I got it now :)
8. ### Understanding energy conservation in a solenoid

Ah sorry, I should have said the potential energy of the magnetic ball.
9. ### Understanding energy conservation in a solenoid

So let's assume ideal wire, resistance = 0 Ohms. Also assume there is a magnetic ball 1 meter away and is attracted to the solenoid. If you have a loop of wire and run a small current through it, you get a magnetic field. This field attracts the magnetic ball, over a distance of 1 meter. If...
10. ### Not understanding work stored in a capacitor

Ok, so dq represents the incremental charge to be applied on the capacitor plate and not an imaginary test charge between the plates? I'm getting my original info from here, first paragraph: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capeng2.html
11. ### Not understanding work stored in a capacitor

Yes, that's where I am getting caught up. For a spring, each small distance you move affects the spring force, and that force is applied specifically for that small distance dx. But for a capacitor, each small charge you add to the plate increases the voltage, but why is that voltage applied...
12. ### Not understanding work stored in a capacitor

I know V = q/c and W = Vq and dW = V dq. But why is Work in charging a capacitor W = integral of q/c dq? q seems to represent a charge on the capacitor plate and dq seems to represent a separate test charge. If I add a charge to the capacitor plate, I take take the resulting votage and multiply...
13. ### Why do sound waves not bounce off of each other?

The reflection would be a wave bouncing off an incoming wave. S predicts you can add the two waves together to get the net wave, and that waves pass through each other. For two different amplitudes, my R hypothesis says the colliding waves will reflect with their original amplitudes, while S...
14. ### Why do sound waves not bounce off of each other?

Yes, this is exactly the mentality that I had when asking this question. Unfortunately, Orodruin's answer went a bit over my head. So here's my thought experiment. We have a sound source producing a soundwave every second (1 Hz), the soundwave travels at 1 m/s, and there is a perfectly...

Ok
16. ### Where does static friction come from in ABS?

Ok, so a perfectly slippery road and the car was in motion beforehand. Makes sense so far then.
17. ### Where does static friction come from in ABS?

Oh, I was referring to a different scenario in that question, sorry. How could the car ever stop in a no-loss situation?
18. ### Where does static friction come from in ABS?

It all makes sense except for how the car translates without tangential force.
19. ### Where does static friction come from in ABS?

Like a wheel spinning on ice just spins in place until it has grip to move forward (translation), which is offered by the tangential force from the road when the wheel pushes the ground.
20. ### Where does static friction come from in ABS?

Can you show me when when I described a car at rest? Let me look at it from a sliding standpoint to see if it's easier for me. A car is sliding left with locked wheels. Kinetic friction by the road pushes to the right. This kinetic friction does two things: tries to spin the wheel CCW and...
21. ### Where does static friction come from in ABS?

I am. Isn't that what we said in #37?
22. ### Where does static friction come from in ABS?

I know the other torque is CW from the brakes, I just didn't mention it. But we also said before the brake torque and road torque to the right counteract each other, so no net torque is applied on the wheels. The rightward force on the bottom of the wheel keeps it spinning CCW, and a CCW...
23. ### Where does static friction come from in ABS?

It will be CCW. But didn't you agree the CCW torque spins the wheel CCW? And also provides a rightward translation force in #41? So CCW wheel keeps the car moving left... but then I assume there's a split between how much force goes to rightward translation force and how much keeps the wheel...
24. ### Where does static friction come from in ABS?

Not sure what you're asking. If the bottom of the wheel is to go left, then the wheel turns CW. If the car is to go left, then the wheel is to go CCW, and CCW is the direction of the torque from the road on the wheel, keeping the wheel spinning. Are you saying then the patch is wanting to move...
25. ### Where does static friction come from in ABS?

So the translation force works to keep the wheels spinning which keeps the car going left, but also slows down the car? How does that work? And if forces come in pairs, what's the other force that makes the road want to push rightwards?
26. ### Where does static friction come from in ABS?

In the context that the road provides translation force, then to stop the car going leftwards, the road has to provide a translation force to the right. But wouldn't this translation force also act as CCW torque on the wheels?
27. ### Where does static friction come from in ABS?

I only typed what I did in post #6 in the context that no-slip MUST be observed. If the brakes apply CW torque, the wheel slows. If the whole car and wheel are translating at the same velocoty as it was before, then there will be slip due to the slowing of the wheels. If the no-slip has to...
28. ### Where does static friction come from in ABS?

Right, the wheel will spin, but it will not translate until it has grip. So the road provides the translation force, I think.
29. ### Where does static friction come from in ABS?

Isn't that how a wheel rolls? A CCW spinning wheel travels to the left because the bottom of the wheel travels rightwards, and the wheel pushes the road with a rightward force. So the road pushes on the wheel with a leftwards force. Also, is this correct: A rolling wheel with no slip...
30. ### Where does static friction come from in ABS?

Wouldn't the CW torques oppose the CCW motion of the wheel? I don't see how it would accelerate. If I have a rolling wheel with no brakes, then the road is what slows down the wheel, right? If add brakes, then both the brakes and road will slow the wheel.
31. ### Where does static friction come from in ABS?

Sorry, still confused. Is there a difference between a wheel and a tire? *edit* Oh there is. Sorry, not really a car guy.
32. ### Where does static friction come from in ABS?

Ok, I think I might have confused the instantenous V = 0m/s on the bottom of the tire to mean a non-rotating tire. So yes, the tire is rotating. Brakes apply CW torque, and the road does as well. The interaction between the road and tire is static friction?
33. ### Where does static friction come from in ABS?

I'll try to identify both cases just so we're onthe same page. Case 1: The road applies kinetic friction rightwards on the bottom of the wheel, which acts as torque CCW on the wheel. The brakes applies a static friction against the wheel CW, and the wheel remains locked. Case 2: The rolling...
34. ### Where does static friction come from in ABS?

With a non-locked tire, the tire is slowed down by the internal axles by kinetic friction, the applied brakes by kinetic friction, and the road pushing leftwards on the bottom of the CCW spining wheel. The bolded part is my confusion. The contact patch is in the regime of static friction now...
35. ### Where does static friction come from in ABS?

Sorry, is the bolded part a typo?
36. ### Where does static friction come from in ABS?

Sorry, I meant to say the contact patch doesn't seem to be applying any forces against the road. It has no velocity relative to the road so it's not sliding, so there's no kinetic friction against it... And there's no static friction against it since there's no force leftwards. A car with...
37. ### Where does static friction come from in ABS?

But the tire isn't pushing on the road because the that contact patch has no velocity from the road's perspective, right? So let me try to compare the contact patch that is not moving relative to the ground, and a block sitting on the road. I push the block with a force lower than the maximum...
38. ### Why do sound waves not bounce off of each other?

I know they have to collide to create the next pressure wave, but I don't see why a wave is suddenly a new construct diferent from what it's made of.
39. ### Why do sound waves not bounce off of each other?

Is there an explanation of the principle of superposition in a sound wave? I know it works for waves in general but I'm trying to understand it in a physical way.
40. ### Why do sound waves not bounce off of each other?

If air is made up real little particles, then why would the waves made up of these particles not bounce off? Here's my attempt at an explanation for the principle of superposition for soundwaves. The wave is transferred by the air molecules hitting the ones adjacent to it. But because air is...
41. ### Where does static friction come from in ABS?

It's becoming clearer, but now my question is what is enforcing the no-slip condition, and how does this stop the car? If the brake pads create CW torque, and the ground creates CCW torque of same magnitude, which is required to maintain no-slip, then essentially no torque is acting on the...
42. ### Where does static friction come from in ABS?

Can you go step by step how the static friction "exists" if the contact patch is not accelerating to the left, and how the static friction prevents the wheels from stopping? If anything, it seems like the static friction helps to oppose leftwards translational acceleration, but doesn't do...
43. ### Where does static friction come from in ABS?

Ok, so assume we have a wheel on the road traveling to the left. The wheel spins CCW and also has translation to the left. If we let the wheel roll, assuming no slip, then the translation velocity to the left will counteract the rotational velocity to the right at the bottom of the wheel, so...
44. ### I Breakdown of Gauss' Law?

I'm not an expert and it's a dead thead but I want to state my thoughts anyway. Isn't Gauss's Law responsible for finding the E-fields at the boundaries of the enclosed volume due to the ENCLOSED charge? So due to the almost infinite amount of charge in our volume (let's say a sphere), we can...
45. ### Transmission line voltage delay

Sorry, I was trying to draw a parallel between what happens in a vacuum vs a wire since I thought a vacuum would be easier to analyze. To your question, the answer should be no because there is a voltage propagation delay between the signal port and the one a distance away, and my book says...
46. ### Transmission line voltage delay

The voltage value on a wire a distance away from the signal-port (where we apply the initial voltage) has a phase delay because the current takes time to travel down the wire. But how do you visualize this? First we have a voltage at the beginning, and that causes current to flow. Then a...
47. ### Magnetic flux in solenoid

In a solenoid of N loops and uniform magnetic field B, the magnetic flux is B*N*A, where A represents the area surrounded by each loop. I see that the N comes from the fact that you have one A for each turn, and you have N turns, so the total "area" is NA, but why do we use this? Why isn't...
48. ### I How does the Vector Laplacian come about?

I see, so the definition of the Laplacian of a Scalar is different than the definition of the Laplacian of a Vector, but they use the same notation?
49. ### I How does the Vector Laplacian come about?

Thanks. How do we know this, though? Is it just definition?
50. ### I How does the Vector Laplacian come about?

Sorry Metmann, that is way beyond me.