why does a satellite need no fuel to go around a planet in its fixed orbit ?

Answer 1

u require the satellite to have fuel only for putting into the orbit of the planet around which it needs to revolve. once the satellite is sent into the atmosphere at a sufficient height above the planet (which can be calculated using classical mechanics considering the gravitational field theory of newton) it is imparted a horizontal velocity because of which it is set into a circular motion. see, this component of velocity is very much required for the satellite to undergo a circular motion as then only the gravitational force acting on the satellite acts as a centripetal force which is essential for everybody to undergo a circular motion.and once it starts revolving in a circular motion , it doesnot require any fuel as then the required fuel(centripetal force) is provided to the satellite by the gravitational force.

Answer 2

For a satellite, in fixed orbit, the entire gravitation force (GF) between earth and satellite is matched by the centripetal force (CF) of the circular motion. In other words, entire GF is compensated by CF.

so Net force on satellite = GF - CF =0

An object spends fuel or energy when it has to move against some finite force other than ZERO (that is when object does the work). Here satellite is not doing any external work.

And satellite is only following the Newton's 1st law of motion (inertia due to motion) under the absolute null of force.

An object will remain in the state of rest or will continue to move in circular orbit unless some net external force is applied.

Happy questioning

Answer 3

A satellite going around a planet has its total energy negative, I.e. the potential energy due to force of gravitation ( which is negative) is more than the kinetic energy of the satellite ( which is positive and by virtue of of the satellite). Thus the satellite is 'bound' in its orbit. If some more kinetic energy is given to it ( e.g. by firing a rocket attached to it) so as to increase its total energy to zero, it would just escape the gravitational field of the planet ; if its kinetic energy is more than that it would fly off the planet. So when it is bound to the planet and goes round it, its potential energy is predominant and it is'freely falling' into the planet. But this is just critically falling or trivially falling into the planet. Obviously do we really need some outside energy or fuel for that matter for keeping something falling ?

Answer 4

hello friend ,
i think ur question is why it's tengential velocity is not decreasing if no fuel is being burnt to move it tangentially..
so ur answer is in the newton's 1 st law of linear motion...it states " if a body is moving or stationery,it will keep doing so till an external force is not applied to disturb it.." so in the tangential direction of the satelite no net force is acting so it will keep moving with the velocity it was given at the starting of its motion in the orbit.
although towards the centre of earth , attraction force by the earth on satelite is working which is making it revolve around earth and acting as centripetal force necessary for its revolving motion.

Answer 5

If you threw an object horizontally, it will fall towards the earth and hit the ground. Imagine that you are at a great height from the surface of the earth, and then you throw that same object: it may just fall around the earth without hitting its surface.

A satellite is therefore considered as a free falling body and it falls around the earth at a particular speed depending on the height.

Answer 6

if the horizontal velocity is equal to the critical velocity then satellite moves in circular path &do not need fuel

Answer 7

on earth we need the fuel, because the amount of friction is very high as compared to that in the space so it don't require any amount of energy to keep on moving. it can keep on going with help of it's initial kinetic energy.