Simple pendulum inside a free-falling lift

[devcathk]

Simple pendulum is said to be not applicable if it's in the space that far from other planet which there're no gravitational field present.
Howerver when the system is inside a free falling lift, isn't the bob of the pendulum experience an accelration with value equals to g?
Is it correct to think in this way that the weight of the bob of the simple pendulum is entirely used to provide the acceleration, thus there's no component of weight (mgsin0) to provide the force for the simple pendulum to work, and the bob is considered to be of zero gravity?
For an astronaut oustide the space expereince weightless, there are no normal reaction acting on the astronaut is because of the astronaut is not in touch of a surface or is that it's weight is used to provide the centripetal force?

 

[jbsteele]

Yes, the bob of the pendulum will experience an acceleration equal to g in a free-falling lift. However, this does not mean that the weight of the bob is entirely used to provide the acceleration. The force required for the pendulum to work is provided by the tension in the pendulum string, not by the bob's weight.For an astronaut outside in space, they experience weightlessness because they are far away from any large objects that would produce a gravitational field. Since the gravitational force between two objects decreases with distance, the astronaut is not close enough to another object with a large enough mass to produce a significant gravitational field. This lack of gravity means that the normal reaction force that would normally act on the astronaut is not present.