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1. ### B The principle of relativity

hi everyone "The principle of relativity: The laws of physics are the same in all inertial reference frames." Is in classical physics The laws of physics aren't the same in all inertial reference frames!? Give an example in classical physics Thanks
2. ### B Understanding the Doppler Effect at an Angle

hello everyone How is the sound Doppler effect formula in the case where the movement of the source and the observer is at an angle?
3. ### B The principle of the constancy of the speed of light

hello everyone According to Einstein's second principle of relativity: "The principle of the constancy of the speed of light: The speed of light in free space has the same value c in all inertial reference frames" Does free space mean vacuum? Is this principle not valid in the air and the...
4. ### B Doppler effect on electromagnetic waves in a car

Is the doppler effect on electromagnetic waves receive by cell phone in fast car and so somebody talk with cell phone in fast car view this effect
5. ### I Speed faster than light speed in a medium

Are the formulas of relativity not applicable in the material environment or are they only in vacuum?
6. ### I Speed faster than light speed in a medium

hello everyone I read this text in physics book: "Another example is the so-called Cerenkov radiation, which consists of light waves emitted by charged particles that move through a medium with a speed greater than the phase speed of light in that medium. The blue glow of the water that often...
7. ### I A spaceship with a speed close to light (gravity law)

From the reference frame of the star, the spacecraft has a lot of mass, so it must interact gravitationally.
8. ### I A spaceship with a speed close to light (gravity law)

A ship that moves at a speed very close to light, its relative mass increases and may be comparable to the mass of the planets or the sun, in this case it can change the orbit of the planets and the sun (according to the law of gravity of two bodies) Is this analysis correct?
9. ### B Our Sun's position in the Milky Way Galaxy

Is this sentence correct? Our Sun lies in one of the spiral arms of the Milky Way, about 2/3 of the way out from the center of the galaxy.

11. ### B How does the Milky Way galaxy move in the local Group?

How does the Milky Way galaxy move in the local Group? Is there a circular motion around the center of the local Group like the sun moves around the center of the galaxy?
12. ### B Newton's second law about cars

F_t act on road so you should remove this force because they don't act on car. do F_R cause e force produce anti-rotational torque
13. ### B Newton's second law about cars

Ft is acting against the F'R
14. ### B Newton's second law about cars

The reaction force can be balanced by friction so there is not force to accelerate car! isn't it?
15. ### B Newton's second law about cars

what is F'R ?
16. ### B Newton's second law about cars

can you plot a free body diagram (FBD) and forces in car and and explain the below equation?
17. ### B Newton's second law about cars

When a person walks, it is clear that an external force enters the sole of the foot from the ground and agrees to move in that direction, but in the case of a car, where is the direction of the reaction force and where does it enter?
18. ### B Newton's second law about cars

The car that accelerates must enter according to the equation below the external force, while such an external force does not seem to exist. The force of friction between the car and the road is in the opposite direction of motion ؟
19. ### I Conservation of angular momentum -- spinning a bicycle wheel in space

Suppose we have a rotating body like a bicycle wheel in space away from gravity. This body stops after a while due to friction between the wheel and wheel axles. Is not the conservation of angular momentum violated?
20. ### B Rolling without slipping in non-sloping surface

because the motion is negative acceleration not possitive acceleration
21. ### B Rolling without slipping in non-sloping surface

This diagram is probably correct because friction reduces rolling, but it contradicts Newton's second law.
22. ### B Rolling without slipping in non-sloping surface

Consider two modes, one with low friction and the other with more friction The rolling body travels longer distances on the surface with less friction.
23. ### B Rolling without slipping in non-sloping surface

Given that the motion is rolling, it means that the friction is non-zero. Like a ball dropped on the ground.
24. ### B Rolling without slipping in non-sloping surface

but in free-body diagram, the friction force decrease velocity, isn't it?
25. ### B Rolling without slipping in non-sloping surface

Suppose we leave an object on a non-sloping surface that rolls and moves forward without slipping. Does this object continue to move indefinitely?
26. ### I Question about the expanding Universe and the Andromeda Galaxy

I mean, in addition to the gravitational expansion or dark energy, the Andromeda Galaxy's calculations have to be included in the calculations.
27. ### I Question about the expanding Universe and the Andromeda Galaxy

Overall, I came to the conclusion that the gravitational bond of these two galaxies overcomes expansion.
28. ### I Question about the expanding Universe and the Andromeda Galaxy

According to Hubble's law, the Andromeda Galaxy should move away from us at a speed of about 55 kilometers per second, but on the contrary, the galaxy is approaching us at a speed of 110 kilometers per second!
29. ### I Question about the expanding Universe and the Andromeda Galaxy

Hi If the universe is expanding, then why does the Andromeda Galaxy approach us? Does not it contradict Hubble's law?
30. ### B Is the weak nuclear force attractive or repulsive or both?

" weak interaction, is responsible for certain types of particle decays" That is, if this force does not exist, the particles will not decay. Pay attention to this sentence The weak force between two neighboring protons is about 10^-7 of the strong force between them, and the range of the weak...
31. ### B Is the weak nuclear force attractive or repulsive or both?

this is not useful
32. ### B Is the weak nuclear force attractive or repulsive or both?

Does this force act as repulsive or attractive? How does this force act in decay? Is it large and directional?
33. ### B Is the weak nuclear force attractive or repulsive or both?

Hi Of the 4 fundamental forces, I did not understand the weak nuclear force. Is the weak nuclear force attractive or repulsive or both? It works between two particles, that is, it is the interaction of two particles?
34. ### I Question about Kuiper belt

According to this image, the density of the Kuiper belt is much higher than that of the asteroid belt My question is, what is the average distance of objects in the Kuiper belt?
35. ### I Question about Kuiper belt

What is the distance between the objects in the Kuiper belt? Is the density of objects high and the probability of a spacecraft colliding with objects in this area?
36. ### I Questions about the Voyager spacecraft

To travel to interstellar space requires the final speed and highest speed without return and slow down.
37. ### I Questions about the Voyager spacecraft

A spacecraft with as much fuel as possible can reach any speed. For example, if the spacecraft 's fuel is 10^9 kg, it results in the simplest case, that is, the conservaton of the momentum for the variable mass.(extremely high speeds of the ejected ions=50 km/s) vi=0, Mi=10^9 kg, Mf=10^3 kg...
38. ### I Question about Earth's rotation

I want angular frequency of Earth at this moment but I can't find it on Google ω=2(pi)/86400=72.7221*10^-6 (difference every moment)
39. ### I Question about Earth's rotation

Thanks What did you search on Google that led to this result?
40. ### I Question about Earth's rotation

The period of rotation of the Earth around itself is changed by seasonal winds, tides, and other factors. The exact amount changes daily(about nano second). Is there a website that shows this amount?
41. ### I Questions about the Voyager spacecraft

What is the speeds of the ejected ions? Does it need an atmosphere or does it work outside the atmosphere?
42. ### I Questions about the Voyager spacecraft

That is, with more energy storage that can communicate with the Earth for up to 100 years, also with a better design that has a faster speed in space.
43. ### I Questions about the Voyager spacecraft

Does NASA plan to produce faster, more fuel-powered spacecraft ? Replacement for Voyager 1 ع
44. ### I Questions about the Voyager spacecraft

Missile systems work with a mass reduction mechanism (due to the exit of mass from inside it) that causes acceleration. Can not this mechanism be implemented in spacecraft ?
45. ### I Questions about the Voyager spacecraft

Is it due to the lack of oxygen outside the Earth's atmosphere?
46. ### I Questions about the Voyager spacecraft

Is there a possibility of a celestial body colliding with the Voyager spacecraft ? Is there an alternative to the Voyager that runs faster and faster? For example, at a speed of 100 kilometers per second
47. ### How can there be neodymium magnets when neodymium is paramagnetic?

Neodymium is a paramagnetic material, so how do we have a permanent neodymium magnet?
48. ### I Orbital magnetic dipole moment of a proton

hi every one what is the amount of orbital magnetic dipole moment of proton? this different with the intrinsic magnetic.