Answer to Question #6192 in Mechanics | Relativity for Oscar Carlsson
How much power P [W] is needed to force a satellite (modeled as a point particle) to move in a perfect circular orbit with radius r [m]? The mass of the satellite is m [kg] and its tangential speed v [m/s] is constant.
- It is assumed that NO GRAVITY affects the satellite!
- The mass loss due to fuel consumption is neglected.
- The power is assumed to act under ideal conditions, i.e. there is no energy loss due to friction or the choice of engine.
- Relativistic effects are neglected.
I have received many answers saying that P = 0 as a consequence of the definition of mechanical work. But this cannot be true since no gravity affects the satellite. Energy is needed to create a force that changes a linear path in space and a circular orbit is one such motion. In absence of gravity no particle with mass will loop in a circle without any energy.
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