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can some kind of high-powered light beam offer a means of propulsion?

The fundamental question I’m trying to ask is, can some kind of high-powered light beam offer a means of propulsion?Let’s say you have a twelve-pound probe with a light source as an engine, and a near infinite amount of energy to power it.If this light emitting engine could be illuminated to be as bright as the combined omni-directional light of a star – or perhaps a supernova – and focused into a very finite stream of photons like an extremely high-powered laser, would your probe accelerate in the opposite direction than the beam is being emitted from in relation to an object that was once moving through space at the same velocity as your probe?
Asked Gabriel

Electrostatics HOTS for Practice

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Revise Electrostatics online – Fast Revision module for class XII

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Electricity from ocean currents

How can we produce electricity using currents in ocean?

Asked Saurabh Pathak


Electricty can be generated from ocean through various means, mainly

  • Ocean Thermal Energy Devices
  • Tidal Energy
  • Energy of waves and
  • Ocean Currents

The energy extraction from ocean currents is somewhat analogous to energy from winds. (ref http://www.boem.gov/Renewable-Energy-Program/Renewable-Energy-Guide/Ocean-Current-Energy.aspx)

Ocean current technology is still in its early stage of development.

For ocean current energy to be utilized successfully at a commercial scale, a number of engineering and technical challenges need to be addressed, including:

  •  avoidance of cavitations (bubble formation);
  •  prevention of marine growth buildup;
  •  reliability (since maintenance costs are potentially high); and
  •  corrosion resistance.
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Path dependence of Thermodynamic Variables

In NCERT TEXT BOOK it is written that
Since U is a state variable, ΔU depends only on the initial and final states and not on the path taken by the gas to go from one to the other. However, ΔQ and ΔW will, in general, depend on the path taken to go from the initial to final states. From the First Law of Thermodynamics,it is clear that the combination ΔQ – ΔW, is however, path independent.

ΔQ and ΔW will, in general, depend on the path taken ??andΔQ – ΔW, is however, path independent.
explain?? how??

Asked Krishan Billa


Determine unknown frequency with the help of beats

Two frequencies sounded together produce 3 beats per second.If one of the frequencies is 400 vibrations per second,the other frequency will be?


Asked Tayyab Mynir




Beating Frequency


There are two possibilities because the beat frequency is equal to the difference in frequencies of the two sounding bodies.


So, the unknown frequency can be either 397 Hz or 403 Hz. This can be verified by lagging/ loading one of the sounding bodies.


Read more at http://en.wikipedia.org/wiki/Beat_(acoustics)


Cambridge QP

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