# Search results

• Users: nasu
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1. ### Electric field generated by solenoid

@quarkyphysicsgirl What is the context of this problem? Is it from an introductory physics course? When they say "long solenoid" it is supposed to be an indication that the formula for ideal solenoid is used. The point indicated (4.54 cm) it is outside the solenoid (radius is 2.08 cm) and the...
2. ### Superposition of two one-dimensional harmonic waves

You are right, he got the right form in post #3, not #1. From this one he can find the positions of maximum amplitude.
3. ### Superposition of two one-dimensional harmonic waves

You don't need all this. You already had the formula for the sum in post #1. All you had to do was to identify the amplitude.
4. ### Superposition of two one-dimensional harmonic waves

The amplitude is not time dependent. It should be a fixed value for a given position, x. Everything that multiplies the time dependent term is the amplitude.
5. ### Initial speed of an object launched from Mars

The radius (r) is given in km, isn't it?
6. ### Solar System Forces -- Simulating the planetary orbits for my project

How do you get this number, 99.99% ? Is this a checked fact or just an impression?
7. ### Finding the work done by a block

The distance traveled is not vertical and is not due to motion with acceleration g.
8. ### I Applications of Virtual objects

Who said it's nonsense? I asked because I never heard about it and not to challange you.
9. ### I Applications of Virtual objects

What is a lenticular screen? It used to be just a white wall.
10. ### B What is the principle of a magnet?

Why dismiss the matter of fact part? If magnetism were not a fact nobody would have bothered to try to make a model of it. There would had been to "it" to start with.
11. ### Calculate the induced EMF of a rotating loop

What do you think is this ξ in the formula shown by BvU? You seem to know it too.
12. ### B Ambiguity in Avogadro's Law?

How do you get the factor of 2 for density (in the second paragraph)?
13. ### Vector-Force image and resolve force

Actually, both pairs are technically called "components". The ones obtained by projection on the two axes are the contarvariant components and the other ones are the covariant components of the vector. Only for orthogonal axes they are the same. But we are so used to the orthogonal case that is...
14. ### Vector-Force image and resolve force

@sHatDowN What is the source of this question? From where did you get the image you posted in the OP?
15. ### Electric Field Inside Cylindrical Capacitor

@OP. What do you think is the magnitude of the field produced by the outer charge inside the cylindrical shell?
16. ### Vector problem, magnitude of the force

The horizntal component is given as 1237 N. "N" is the unit for force in SI, newton.
17. ### Energy conservation law question with capacitor

First, there is no "delta W". The work (not change in work) is equal to the change in kinetic energy. This is because the work is a quantity that describes what happens in a process, in the transition from initital to final state. The kinetic energy, on the other hand, is a quantity that...
18. ### Finding the work done by Spiderman

Forget about it. How much work do you when you walk 6 m horizontally?
19. ### I Neil deGrasse Tyson on Nikola Tesla and electromagnetic energy

But it is 60 Hz, isn't it? The wavelength is of the order of thousands of kilometers.
20. ### Finding the work done by Spiderman

"Equilateral" means all sides are the same size (equal sides). You don't need to split it and to form right angle triangles. You seem to have a tendency to pick the most complicated ways to solve things., 😃
21. ### Finding the work done by Spiderman

That angle is 60 degrees but the extension of the black line is not along the dotted line that you show in the previous drawing. You see here that the black line is not at 90 degrees relative to this dotted orange line.
22. ### Finding the work done by Spiderman

No, there is not. What is that dotted orange line? If you draw it perpendicular ot the direction of ##\Delta \vec{r} ## then the other angle is not 60 degrees. But you don't need that dotted line. Just draw the weight where ##\Delta \vec{r} ## starts.
23. ### I Neil deGrasse Tyson on Nikola Tesla and electromagnetic energy

The potential difference between two points a few centimeters apart on a cable with very low resistance is very small. Typical currents in high voltage power lines are given as few thousand amperes (I found 4000 A value quoted for the very high voltage lines) to few hundred amps in the secondary...
24. ### Finding the work done by Spiderman

There are no 90 degrees angles, as you mistakenly show in your first diagram. How can you get 150?
25. ### Finding the work done by Spiderman

Actually is equilateral, isn't it?
26. ### Finding the work done by Spiderman

You have a triangle with two equal sides (length of the wire in the two positions) and 60 degree angle at the top. What are the other two angles?
27. ### Solving kinematic formula for t

So, you are asking if you can solve a quadratic equation without using the quadratic formula? Or it is something else?
28. ### I Understanding cymatics physics

Yes, the plate and the boundary conditions. You can easily find the vibration modes calculated for plates with free edge, clamped edge or "simply supported". By "easily find" I mean in books or papers. To calculate them is quite a job. They have different patterns and different frequencies even...
29. ### Question about two elastic collision formulas

"Conserved" means same value before and after a process (or just a at two different times). It applies to state parameters like energy, momentum, angular momentum. Work is a process parameter and "conservation" does not apply to it. You don't have a work before the collision and another after...
30. ### Describing path of the object in an xy plane

The coordinates satisfy the equation of such a circle. This is how they know.
31. ### I Understanding cymatics physics

The resonant frequencies are specific to the plates and do not depend on the frequency of the driver. They are the frequencies corresponding to the normal modes of vibrations. The plate vibrates with the frequency of the driver, as any forced oscillation. As you change the frequency of the...
32. ### I Understanding cymatics physics

The resonant frequencies will be different. The shapes may or not be different. You see the shapes when the frequency of the vibrating device is close to one of the resonant frequencies of the plate. You may see the same shape (or similar) on different plates, but at different frequencies. The...
33. ### I Understanding cymatics physics

The frequencies of the modes depend on the density, shape and size of the plates. And the stiffness too.
34. ### Rotational inertia of square about axis perpendicular to its plane

Won't be easier to just find the moment of inertia for a square of side L and mass m and then use the results for any value of L and for any way this side is related to another parameter in the problem, like to the radius here? You can do this in two or three lines, even by using the integral...
35. ### Rotational inertia of square about axis perpendicular to its plane

You need to put some parantheses inside the integral. Otherwise it does not make sense.
36. ### Rotational inertia of square about axis perpendicular to its plane

##\lambda R^2 ## does not have the right dimension to be a term in the moment of inertia.
37. ### I Question on Hall Effect and magnetic force

If you have both types of carriers they have different drift velocities (different mobilities) so the Hall voltages don't cancel out even if they have the same concentration. In doped semiconductors they have both different concentrations and different mobilities
38. ### Rotational inertia of square about axis perpendicular to its plane

You can do this without extra integrals. You can calculate the moment of inertia of one of the sides around the center by using the parallel axis theorem. You know the moment of inrtia about an axis going through the middle of the side. ##I=\frac{1}{12}ma^2## where m is the mass of one of the...
39. ### Intensity of a wave at half amplitude and twice frequency compared to a reference wave

You know that this is related to some chapter in a book where a specific type of wave is described. Possibly just a plane wave in 1 dimension. But this is not the only wave possible and a linear dispalcement (position of particle) is not the only parameter used to describe a wave. What you know...
40. ### I Distance traveled by a ball down a ramp and on a flat path

How do you know that loss1+loss2=loss? What formulas do you use for these terms?
41. ### Intensity of a wave at half amplitude and twice frequency compared to a reference wave

It does matter to know what quantities are represented on the axes. You may know it but out of context is not obvious.
42. ### Intensity of a wave at half amplitude and twice frequency compared to a reference wave

What kind of wave is this? And what is x on the vertical axis? Is it linear displacement of the particles in the wave?
43. ### I Class debate: Everything we see is a result of reflected light

I am trying to find this description in astrophysics textbooks but did not find it so far. Do you have a reference to textbook on stellar interior describing this bouncing of photons through the solar/stellar interior? My original post was based on the suspicion that this is just a pop science...
44. ### I Class debate: Everything we see is a result of reflected light

Then why propagate this image of a photon bouncing like a pinball ball towards the surface and eventually escaping into space? Not all the processes contributing to the opacity of the solar interior are ellastic scattering where you may argue that is the same photon but with the lower energy...
45. ### Finding charge on a capacitor given potential difference across two points

Then this is already labeled as Q total. This is the charge on the upper group of capacitors. And the same charge is on the lower group, which is in series with the upper group. .
46. ### Finding charge on a capacitor given potential difference across two points

What do you label as Q1?
47. ### I Class debate: Everything we see is a result of reflected light

The energy carried by the initial gamma photons reaches the surface after a long time. But the photons themselves? How do you tell that the visible photons are the same as the initial gamma photons? Are the two photons involved in Compton scattering, for example, the "same" photon or are they...
48. ### Discontinuity in an Electric line of force

The field can be discontinous. And actually is across any surface charge distribution. Of course, a really 2D charge distribution does not exist in reality but the disconinuity is a well accepted fact in EM books and the change is even expressed as a function of the charge density. The potential...
49. ### Can you please explain Bernoulli's equation?

Sorry, I did not post anything in this thread. I mean, until now. You mean someone else, I suppose.
50. ### I Class debate: Everything we see is a result of reflected light

The light emitted by the star's surface is made of photons who did no bouncing inside the star. The gamma photons emitted by the thermonuclear reactions don't reach the surface. Even if they did, we won't see them.