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There are two kinds of energy to keep track of: potential energy and kinetic energy. Work can be thought of as the change in energy (because of the "work-energy theorem"). And the key question to ask while the weightlifter keeps his weight in the air is: is there a change in energy? Kinetic energy is a function of movement. If there's no change in ...

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When the weightlifter lifts the mass he does work and transfers some energy to the mass which is stored* in the mass as potential energy. Once the bob has been lifted the weightlifter applies a force to keep the bob lifted (to counter the force exerted by the mass downwards i.e. mg) but does no work as the force does not cause any displacement. Edit: *No ...

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Pu 239 can be put in highly toxic radioactive isotopes. As you know radio isotopes are mostly generated from the radioactive decay reactions and the heaviest material naturally occurring is U238. Pu239 is mostly created in artificial nuclear reactions. The danger of the radio isotopes is measured by their half lives. Radio isotopes having longer half ...

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It's because the centre of buoyancy and centre of gravity don't necessarily lie on the same point. This creates two types of mechanical equilibrium: stable and unstable. It turns out that when a human body is floating with its face inside the water, the body is in stable equilibrium. That is because in that position, the centre of gravity lies below centre ...

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There are two effects at work here to form the Color Afterimage. The blue light stimulates the S-type cone cells most, and they simply "tire out". Local supplies within the cell of ATP become run down, and the cell cannot therefore signal as often or as effectively. When you looked away into a more "balanced" light, white light that would normally fire all ...

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My answer will be very non-technical, but hopefully will convey some basic ideas about what the quantum state (or wavefunction) is about. One intuitive way to picture the nature of the quantum state of a system is to see it as the interference (hence the "wave" idea) of every different changes it could possibly undergo while it is not being messed with. ...

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There are 37.2 trillion cells in a typical human body, (probably a good few more in mine ;), then in each cell there are 20 trillion atoms, then you have to obtain the wave function for each of the electrons....... Actually, it may well be that you cannot describe a wavefunction for a macroscopic object, like a human body. In the study of quantum ...

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This may be slightly more technical then you are after but may be of use to others. There are two things going on here. As mentioned by others you have the separation of charge by a dielectric and hence have a capacitor. If you start of in an electrically neutral situation and move $n$ protons from outside the membrane to the inside a voltage of: V=\...

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Let's say we already have an assembly of 3 static charges, with initial energy $E_0$. In order to place an additional charge, we need to push the charge in, thus applying work (Energy) equivalent to $W_4 = kq_4(q_1/r_{14} + q_2/r_{24} + q_3/r_{34})$ And now, the whole assembly of 4 charges has an additional $W_4$ of energy: $E_{tot} = E_0 + W_4$ This is ...

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It is a bit of a hypothethical scenario where the body can breathe oxygen and does not rupture from the pressure difference (dissolved gases in the intestine and blood bubbling), but at the same time can evaporate and radiate freely. If we assume so, and also assume that there is no sunlight, then there are two major mechanisms for heat loss: radiative ...

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