136,377 reputation
9229379
bio website ratsauce.co.uk
location Chester, United Kingdom
age 54
visits member for 4 years, 4 months
seen 10 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.


1d
comment How to calculate the weight in en elevator going upwards / downwards?
Duplicate of Accelerating an elevator
1d
comment Does “finite” include zero?
No there is no rule. I have been guilty of using finite to mean non-zero, and while I probably shouldn't do this it's ofetn a convenient shorthand. It's normally obvious from the context if the author is (ab)using the term finite to mean non-zero.
1d
comment Finding velocity field of spherical bubble in incompressible fluid
To be fair, the two questions are more conceptual than just about soling this problem.
1d
comment Physical reason behind having greater amplitude when driving frequency$ < $ natural frequency than that when driving frequency $>$ natural frequency
Yes. Even with a slow driving frequency there will be short periods at the turnaround points in the oscillation where the force acts opposite to the direction of motion.
1d
comment Is plasma an intermediate stage of matter?
possible duplicate of Is a plasma a distinct phase of matter?
1d
comment Why isn't any current induced in a rectangular loop when it is moved in a uniform magnetic field with constant velocity?
Atsby, it would be good if you could make this quantitative by writing the equations for the induced EMF.
1d
comment Why isn't any current induced in a rectangular loop when it is moved in a uniform magnetic field with constant velocity?
Not without giving a full answer, and I'm working on a slow and flaky mobile link at the moment. When I get into the office I'll revisit this question if I have time.
1d
comment Why isn't any current induced in a rectangular loop when it is moved in a uniform magnetic field with constant velocity?
I think moving in means moving inside i.e. the coil stays inside the region where the magnet field is constant. If you started with the coil outside the region where the magnetic field is constant and moved it in to this region, then there would be an induced EMF just as there would be when moving the coil out of the region.
1d
comment Why isn't any current induced in a rectangular loop when it is moved in a uniform magnetic field with constant velocity?
Actually, now I think about it, there would be an EMF when moving out of the field even when moving normal to the plane of the coil. When you're moving in a uniform field the field strength is constant so $dB/dt = 0$. However when moving out of the field the field strength is changing so $dB/dt \ne 0$. That's the difference.
1d
comment If you fall in a black hole, when do you go past the event horizon?
possible duplicate of How can anything ever fall into a black hole as seen from an outside observer?
1d
comment Why isn't any current induced in a rectangular loop when it is moved in a uniform magnetic field with constant velocity?
I'm guessing that moving out of the field means moving sideways i.e. in the plane of the coil. Think about how many field lines per second are being intersected by the coil when moving (1) along a line normal to the plane of the coil and (2) along a line in the plane of the coil.
1d
comment Why isn't any current induced in a rectangular loop when it is moved in a uniform magnetic field with constant velocity?
Can you clarify the geometry you're talking about? I'm guessing you mean the plane of the coil is at right angles to the field lines.
1d
comment Can antimatter becomes black hole?
You might also be interested in this question.
1d
comment The spring of air: Why does a piston undergo SHM when it is displaced lengthening the air-column inside a cylinder filled with air?
@user36790: if you pull on the end of a spring and stretch it, the work you do goes into increasing the potential energy of the spring. This is just the same.
1d
comment Do EM waves need a medium to propagate?
There are many, many duplicate and related questions already on the site.
2d
comment Buoyant force on a hollow sphere
If the sphere isn't flexible that means it cannot change size or shape, so by definition the volume cannot change.
2d
comment Hadron Annihilation - what happens with the constituents
It doesn't really make sense to ask. The proton isn't three point like quarks buzzing around in a sea of virtual particles. The quarks are delocalised, and the virtual particles are just a device for representing the energy in the quantum field(s).
2d
comment Work done by a gas in an expansion
See the question I've linked. Physicists tend to be casual about the sign convention for work because it's usually obvious from the context.
2d
comment Hadron Annihilation - what happens with the constituents
If you take for example a proton-antiproton annihilation, Anna posted a bubble chamber picture of the results in her answer to this question. It is a messy business and typically produces a shower of pions.
2d
comment “Shortest” path in general relativity
@ShingLau: if you're asking why the universe is Lorenztian, i.e. why equation (1) applies, I don't think there is an answer. It just is.