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comment How can we know the state of a quantum system?
The position eigenstates are different from the momentum eigenstates for example. So once position is measured, the system is in a position eigenstate, and in a superposition of momentum eigenstates. The values of ci for the momentum eigenstates can be calculated, if we know the relationship between position and momentum eigenstates.
Apr
13
reviewed Approve Will gravity pull together two bodies from the other side of an empty universe?
Apr
6
comment Why are vibrations so common?
@JohnRennie, I liked your comment but I thought the displacement dependent force idea was a good answer to the question.
Apr
6
comment Why are vibrations so common?
@JohnRennie, please don't provide answers in the comment section.
Apr
6
comment Does this length refer to wavelength or length?
@DavidZ, nevertheless I've converted my comment to an answer.
Apr
6
answered Does this length refer to wavelength or length?
Apr
6
comment Does it make sense to add overlapping probabilities > 1?
You can add up whatever you want. It's what you do with the result that matters.
Apr
2
answered How does really the “wave function collapse” work?
Apr
2
comment Is torque necessary in rigid body mechanics?
Thanks for your answer, but I have analysed the scenario in your second paragraph and the answer can again be obtained without torque or angular momentum arguments, but instead making the assumption that component of force in the direction parallel to R will not move the mass, and only the component perpendicular will move the mass. As the mass rotates, the component of force in the direction perpendicular to R decreases (Fp = Fcos(theta)). Therefore a_t = Fcos(theta)/m in using linear mechanics and momentum arguments, where theta is angular displacement of rod.
Apr
2
comment Is there any net external force acting on the universe?
@CuriousOne, just as one can't tell if they are in an accelerating vehicle from the inside?
Apr
2
asked Is torque necessary in rigid body mechanics?
Apr
1
comment Pressure question problem in forming the equation
I can't see where point M is, sorry.
Mar
30
revised Homework: Expression for minimum speed to cause collision of objects / simple kinematics
deleted 175 characters in body
Mar
30
revised Homework: Expression for minimum speed to cause collision of objects / simple kinematics
deleted 175 characters in body
Mar
30
answered Homework: Expression for minimum speed to cause collision of objects / simple kinematics
Mar
30
comment Homework: Expression for minimum speed to cause collision of objects / simple kinematics
Is this homework or something?
Mar
28
comment Could a finite amount of space in the universe exist without time?
@CuriousOne, so it is not scientific to ask whether or not empty space exists if there is no observers there to interact with it? I guess this question belongs in philosophy then.
Mar
28
comment Could a finite amount of space in the universe exist without time?
@CuriousOne, I don't think he is asking if a person can exist without there being clocks, but can a small element of the universe exist without there being clocks? Perhaps a small bit of empty space, or the centre of a black hole?
Mar
17
comment 1st Law of thermodynamics (conservation of energy) and quantum tunneling
deltaEdeltaT>=hbar/2.
Mar
17
comment What is the current big question or motivation in quantum information?
How to build a quantum computer