# Recent content by bgq

1. ### I Acceleration Versus Gravity (General Relativity)

Thank you very much.
2. ### I Acceleration Versus Gravity (General Relativity)

Hi, It is usually claimed that a person in an accelerating elevator with an acceleration equals to the gravity of the earth; this person cannot make any experiment that makes him know whether he is in the elevator or on the surface of earth. However, if this person project two light beams...
3. ### I Determinism of Macroscopic World

Thank you very much
4. ### I Determinism of Macroscopic World

Hi, If the microscopic world is not deterministic, then naturally the macroscopic world should also be not deterministic because it is based on the microscopic world. The problem is that the macroscopic world is deterministic; the evidence of this is that a lot of our technology and...
5. ### Synchronous Sources and Interference

OK, thank you all very much :smile:
6. ### Synchronous Sources and Interference

Actually, I have completed two years general physics in university, I have learned that the sources should be coherent (talking about interference). A student in the secondary school asked me about synchronous. In his textbook (translated from french), they say about the conditions of...
7. ### Synchronous Sources and Interference

Well, is this mean that "coherent" and "synchronous" are the same? Is it just a linguistic issue?
8. ### Synchronous Sources and Interference

Hi, What is the scientific definition of "synchronous sources" when we talk about the conditions of interference? Thank you.
9. ### Hooke's law for vibrating massive spring

Oh, I missed this point. Thanks a lot. I will try to do it again.
10. ### Hooke's law for vibrating massive spring

I don't remember the URL, but here is my work. Let M be the mass of the spring, L is its length at any time t, and V is the speed of its free end at the time t. Let x be the distance from the fixed end of the spring to any infinitesimal part of the spring, and v is the speed of this part. Let λ...
11. ### Hooke's law for vibrating massive spring

Hello, Just for curiosity... Is Hooke's law valid for a vibrating massive spring ? I have done some calculations using both Newton's 2nd Law and the conservation of energy to a horizontal swinging spring connected to a small block in the absence of any friction. I have found that the tension of...
12. ### Doppler Effect and Conservation of Energy

Neither towards nor away. In this case the received frequency would be the same as that sent by the source. Is this true?
13. ### Doppler Effect and Conservation of Energy

I don't have a problem that energy depends on the frame. What confuses me is the example in my previous reply where energy appears not to be conserved with respect to the same frame.
14. ### Doppler Effect and Conservation of Energy

OK, Lets calculate the total energy. Consider a fixed observer standing beside a long road. Now consider a car with a lamp on its roof that produces light of frequency f moving towards the observer. According to this observer, the total energy of the system (Car, light) is E1=1/2mv2 + nhf' where...
15. ### Doppler Effect and Conservation of Energy

Thanks to your reply. Even if the frame does not change (the fixed observer), the energy of the photon will change if the source moves. So the energy changes within the same frame of reference