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when you are inside the bus or jeepney? what do you experience when the vehicle starts from rest, then what do you also experience when the vehicle is moving fast and its stop suddenly? explain this experience in terms of a law inertia

Questions posted via PhysicsFans.com chat

  • In nuclear physics during beta- decay a  proton is converted to neutron,positron and a neutrino. How it’s possible for a proton to decay into more massive neutron. And it’s said that the decay is possible only when it’s inside the nucleus. so whether any other factors is involved in this decay?
  • We study in magnetism that Earth’s magnetism has 3 components namely declination Inclination,Horizontal component of Earth’s magnetic field. What is the cause of declination? Why it changes from place to place?

Weightlessness in a satellite

Guion Bluford Experiences Weightlessness on th...
Guion Bluford Experiences Weightlessness on the KC-135 – GPN-2002-000148 (Photo credit: Wikipedia)


Why does an astronaut feel weightless in a space capsule orbiting the earth?

I’ve gotten a key point saying that the space capsule orbiting the earth has a centripetal acceleration, but I cannot figure out why is it related to the question.


Asked Ganondorf Jallida


Answer: The centripetal acceleration is provided by the force of gravity. Since the force of gravity is completely used up in providing the centripetal acceleration to the space capsule, the astronaut feel weightlessness.



Time Paradox

Question: In Michio Kaku’s book Parallel Universes, it addresses the infinite possibility of a “time river” in correlation with Time Travel and its respective paradoxes. The one is question would be the grandfather paradox, in which if one would travel back in time and dispatch their parents his own future would would be “impossible”.


Alternative version of image:Wooden hourglass ...


It has been suggested than not unlike a fork in the river, his own sequence of events that portray his future would remain unaffected rather the action would invoke a split or fork in the river to extend a parallel future to which he did not exist. Can you please prescribe further insight to this conundrum and any further literature on this subject would be much appreciated. For reference this is discussed on the last 4-5 pages of Chapter 5 in the book.


Asked by Z King


Curvature of Space Time

The curvature of space time would seem to add uncertainty to the position of distant galaxies.  How do we know that a position of a galaxy when appearing to be visabbly in front of us is not, for example, not actually in the opposite direction?

Asked David Sidlowe

Doubts on Induction Cooker working

I’m studying induction cookers
what would happen if i placed 2 or more induction coils in close proximity (say a cm apart) and turned them all on?
and how exactly do zoneless induction hobs work?

what would be required to negate the undesired effects, if any?
also, why do they have only circular coils? can it be rectangular/ triangular?

Asked Rahul

Electronic and Coil inside of an Induction Coo...



Buoyant force concept and terminal velocity? My aerodynamics book(John Anderson Aerodynamics) say that whenever a body moves through a fluid, there are only two types of forces acting on the body. 1. Pressure force that acts perpendicular to the plane of the body and the other is the drag force that acts parallel to the objects velocity.


Forces at Work


Also i read an article that buoyant force is related to static fluids not moving fluids. Now, i was working on a concept of terminal velocity of an object moving through air in the Z direction. According to my concept, the air is continuously in motion and hence its a dynamic fluid. So, accordingly, the body falling through air will experience friction drag parallel to the velocity and pressure force perpendicular to the velocity. But as i was going through the derivation of the terminal velocity, they have counted the buoyant force in which is completely confusing me. If there is buoyant force when the body is moving through a moving fluid then when an aircraft is cruising at an altitude, why do they not mention the buoyant force? Rather they say that the vertical force is the pressure force which is also the lift force. I am really confused when to apply buoyancy and the concept of this pressure force which acts perpendicular to the plane of the body Please help me.


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February 2013

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