Centripetal vs. Centrifugal Forces and Artificial gravity

[jw1985]

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Hi All,

I am having trouble understanding how centripetal force can be used to create artificial gravity. In TBR Physics, Chapter 2, #8, the question discusses how this artificial gravity is created by the net vector forces pointing away [What are these vectors pointing away???], and the normal force of the walls of the space station provide the inward pointing force.

I don't understand how centripetal force can create gravity [which points towards the center of a mass], if the gravity experienced on the space station is a normal force. Wouldn't this mean there must be a force pushing from the center of the spin axis outward to create this normal force?

Thanks!

 

[Gauss44]

Hi All,

I am having trouble understanding how centripetal force can be used to create artificial gravity. In TBR Physics, Chapter 2, #8, the question discusses how this artificial gravity is created by the net vector forces pointing away [What are these vectors pointing away???], and the normal force of the walls of the space station provide the inward pointing force.

I don't understand how centripetal force can create gravity [which points towards the center of a mass], if the gravity experienced on the space station is a normal force. Wouldn't this mean there must be a force pushing from the center of the spin axis outward to create this normal force?

Thanks!

I think the vectors pointing away from the center of rotation in your question represent centrifugal force from the "rider's perspective" as described in this article: http://galileospendulum.org/2011/08/17/centrifugal-forces-and-trojan-horses/

Question #8 in my TBR seems to deal more with the "outsider's perspective" discussed in the article, involving inertia and centripetal acceleration. Not sure if we have the same question or not. My book says: "As a satellite orbits the Earth with uniform circular motion, which of the following conditions must are true?"

When I first read your question, it reminded me of a gravitron.

 

[mehc012]

Hi All,

I am having trouble understanding how centripetal force can be used to create artificial gravity. In TBR Physics, Chapter 2, #8, the question discusses how this artificial gravity is created by the net vector forces pointing away [What are these vectors pointing away???], and the normal force of the walls of the space station provide the inward pointing force.

I don't understand how centripetal force can create gravity [which points towards the center of a mass], if the gravity experienced on the space station is a normal force. Wouldn't this mean there must be a force pushing from the center of the spin axis outward to create this normal force?

Thanks!

Remember, zero-gravity means that you feel weightless. However, the weight you feel, even on earth, is not a sensation of the gravitational force on you...it is just your perception of the normal force pushing up on your feet (or butt, or whatever is on the ground then). On earth, this normal force is present to counteract the downward pull of gravity, lest you sink through the floor. Rather, it is the 'equal and opposite' force to the downward force you exert on the ground...whichever phrasing you prefer.

In space, however, you are correct in that there are no forces pushing you towards the outside of the circle. The term 'artificial gravity' is perhaps not as accurate as 'artificial weight'. However, the floor is accelerating towards you, creating a normal force in the direction of acceleration. Remember that in uniform circular motion, acceleration is always towards the center of the circle.

Just as when you are on an elevator moving upwards, this acceleration towards you increases the normal force the floor exerts on you. The only force which you could accurately say points 'out' of the circle is your normal force on the floor, but that is fairly irrelevant in terms of calculation.