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Is the required thrust 10.8N ?

Quote from: Geezer on 13/05/2010 21:09:39Is the required thrust 10.8N ?I get something a little different... Let me know what you think of my reasoning.Centripetal force is F=mv^{2}/r, so it depends on the square of your velocity. My calculation goes like this: Gravitational force is enough to hold you in orbit at the slow speed. At high speed, your speed increases by a factor of f=84/40. Since the force needed to hold you in orbit is proportional to v^{2}, it increases by a factor of f^{2}. The total centripetal force you need to hold this faster orbit is f^{2}F_{grav}, where F_{grav} is the regular orbital speed when that force is entirely provided by gravity.Therefore, the extra force you need is: (f^{2}-1)F_{grav}.Since the normal force of gravity at the earth's surface is 9.81 N for a 1 kg mass, the extra force required will be roughly 33.45 Newtons.

Although the construction of a frictionless inverted railtrack under which he could orbit would be a convenient way to keep him orbiting once he had got up to speed in the absence of such a track he would need to provide a continuous thrust directed away from the Earth to avoid flying out of orbit.This would of course would require the expenditure of energy, how much ?.

Now that calculators and computers are readily available I do not think there is any need to cook the questions to make the arithmetic easy.

Still none.Work = force times distance.No matter what force you end up calculating, since Puck remains at the same height that force acts through no distance so the work done is zero.Since, as you have accepted, a rail could provide the force you have to ask how much work can a lump of metal do?Can it provide any energy? If so then you have solved the world's energy crisis.The only extra energy needed is because to go round the world quicker, Puck moves faster and has more kinetic energy. Calculating that is trivial as long as you know the size of the Earth.

Quote from: Bored chemist on 14/05/2010 07:15:22Still none.Work = force times distance.No matter what force you end up calculating, since Puck remains at the same height that force acts through no distance so the work done is zero.Since, as you have accepted, a rail could provide the force you have to ask how much work can a lump of metal do?Can it provide any energy? If so then you have solved the world's energy crisis.The only extra energy needed is because to go round the world quicker, Puck moves faster and has more kinetic energy. Calculating that is trivial as long as you know the size of the Earth.I think Syhprum is saying no rail is allowed. However, as he didn't specify the radius of the orbit, can we assume a reduced radius for the faster orbit so that the only centripetal force is provided by gravity so that no rail is required and no work is done?

Quote from: Geezer on 14/05/2010 07:27:22Quote from: Bored chemist on 14/05/2010 07:15:22Still none.Work = force times distance.No matter what force you end up calculating, since Puck remains at the same height that force acts through no distance so the work done is zero.Since, as you have accepted, a rail could provide the force you have to ask how much work can a lump of metal do?Can it provide any energy? If so then you have solved the world's energy crisis.The only extra energy needed is because to go round the world quicker, Puck moves faster and has more kinetic energy. Calculating that is trivial as long as you know the size of the Earth.I think Syhprum is saying no rail is allowed. However, as he didn't specify the radius of the orbit, can we assume a reduced radius for the faster orbit so that the only centripetal force is provided by gravity so that no rail is required and no work is done?We'd be inside the earth! Then we might be eaten by mole people!

JPYou raised a very relevent point ie the efficiency of the propulsion system, I had not considered this and had unconsciously assumed 100%, maybe Puck could use a photon drive or something similar

Where are you putting all this energy you are all talking about?

Puck does a constant speed but it is velocity we are concerned with energy is constantly required to divert his natural hyperbolic path that would take him out Earth orbit to a circular one around the Earth

I did only ask how much power was required not how it was generated.