94,115 reputation
3125232
bio website ratsauce.co.uk
location Chester, United Kingdom
age 53
visits member for 3 years, 6 months
seen 5 hours ago

Semi retired old time computer nerd who started programming on a Commodore Pet.

Since I'm also active in the Physics forum I should add that I started as a theoretical chemist, moved into solid state photochemistry and finally worked in industry as a colloid scientist. I only became a full time computer nerd in 1997.


Jul
18
comment How to find the force to cause certain trajectory?
The Hyperphysics section on trajectories has an excellent description of how to do the calculations you describe. This is quite a large page (well, set of pages) but I think you'd find it interesting. You're quite correct that 45° is a special case and gives the maximum range.
Jul
18
comment How many atoms does one need to get reliable crystal information with X ray or electron diffraction?
@YungHummmma: yes, quite true, but you would still (in principle) measure a diffraction pattern from your two atoms. In fact for amorphous systems you do get a diffraction peak corresponding to the nearest neighbour distance i.e. basically diffraction from pairs of atoms.
Jul
18
comment GPS Satellite - Special Relativity
Making up some numbers to illustrate, suppose $1/\gamma_e = 0.8$ for the Earth's surface and $1/\gamma_s = 0.6$ for the satellite. That means when 100 seconds pass for the stationary observer 80 seconds pass on Earth and 60 seconds pass on the satellite. So as seen from Earth 60 seconds pass on the satellite for 80 seconds on Earth, and the time dilation is therefore 60/80, which is simply $\gamma_e/\gamma_s$.
Jul
18
comment When you measure position of an electron in a energy pure state, what happens to the energy?
Yes, energy is exchanged between the electron and the measuring system, so the energy of each changes. The total energy of both the electron and the measuring system is still conserved.
Jul
17
comment Another layman blackhole question, pulling one end of a string out from behind the event horizon
The downvote is surprising. This isn't the clearest answer I've ever seen but everything M. Herzkamp says is true.
Jul
17
comment Does time move slower at the equator?
@michael: yes, but both the observer at the North Pole and at the equator are moving round the Sun/round the Milky way/along with the Milky Way at the same speed, so these motions do not contribute to their relative time dilation.
Jul
17
comment Another layman blackhole question, pulling one end of a string out from behind the event horizon
As long as you stay above the event horizon you can hover above a black hole using a rocket. You don't have to orbit. In fact there is no stable orbit for matter within 3 times the horizon distance.
Jul
17
comment How many atoms does one need to get reliable crystal information with X ray or electron diffraction?
Are you sure the insets were X-ray diffraction and not electron diffraction? Since TEMs can routinely do diffraction measurements it seems more like they were electron diffraction.
Jul
17
comment Queries regarding the peer review process and examples of where it has not worked out
This question appears to be off-topic because it is not about Physics, it's about fraudulent physicists.
Jul
17
comment How to understand “accelerating charge radiate” using intuition?
The link I've suggested has a reasonably clear description of the process, but this won't be of any help in understanding generation of gravitational waves. Acceleration is described completely differently in GR.
Jul
17
comment How to understand “accelerating charge radiate” using intuition?
possible duplicate of How EM waves are produced by accelerating charged particles?
Jul
17
comment Gravity on flat object
@DavidHammen: the last question is unrelated to the first two and should be posted as a separate question.
Jul
17
comment When you measure position of an electron in a energy pure state, what happens to the energy?
The electron and measuring system wavefunctions become entangled and can no longer be described separately. After decoherence you will once again have separate electron and measuring system wavefunctions, but both will have been changed by the interaction so the electron will no longer be in it's original pure state.
Jul
16
comment Gravity on flat object
The duplicate, and rmhleo's answer only give the field at the centre of the flat surface. The strength of the field when standing in the middle of the rim is still an open question.
Jul
16
comment Gravity on flat object
@KyleKanos: oops, thanks :-)
Jul
16
comment Gravity on flat object
Your Q2 is unrelated to Q1 and should really be posted as a separate question. Actually I think it's an interesting one and the answer is not at all clear to me.
Jul
16
comment Determine the number of days with North-East wind direction from the number of days with North and East wind direction?
@CarlWitthoft: damn, I didn't think of that. I'll update my answer immediately :-)
Jul
16
comment Do all the electrons form Cooper pairs at absolute zero?
Do you mean all electrons in the conduction band?
Jul
16
comment Force to stop a moving rope vs. stagnation pressure of a fluid
Can you provide a link for your equation $\tfrac{1}{2}\rho v^2$?
Jul
15
comment Can an object reverse its direction of acceleration even though it continues to move in the same direction?
@OrangeDog: the net vertical force is small and tends to zero as the amplitude of the swing tends to zero. Remember that the net vertical force is the string tension minus the gravitational force. The gravitational force is indeed straight down, but the string tension is not. The net force, and hence net acceleration, of the bob is mostly horizontal as I've drawn it. It's true the velocity changes throughout the swing, but I've drawn only a small part of the swing over which the velocity is approximately constant.