Which physical law or principle explains why an astronaut inside an orbiting spacecraft experiences a sensation of weightlessness?

💡 Solution & Explanation

An orbiting spacecraft and the astronaut inside are in a continuous state of free fall towards the Earth under gravity, with the gravitational force acting as the centripetal force required for orbital motion. Because both the spacecraft and the astronaut accelerate downwards at the same rate, there is no normal reaction force between the feet of the astronaut and the floor of the cabin, creating apparent weightlessness. Buoyancy, fluid pressure, and gas laws govern entirely different physical phenomena unrelated to orbital mechanics.