Centrifugal force and artificial gravity

In summary: Yes, you feel a force pushing you outwards because the floor is not providing the centripetal force to keep you turning. Without that force, your body would move in a straight line, and you would be pulled away from the turntable.
  • #1
autodidude
333
0
In lecture 5 of MIT's OCW 8.01 , Prof. Lewin says that when you're in in uniform circular motion, the perceived gravity is always in the opposite direction as the push or pull (so if you're holding onto the end of a rope that's being spun around horziontally, the rope is pulling on you and you feel gravity in the opposite direction).

My question is does this perceived gravity have anything to do with Newton's 3rd law? If the rope is pulling on you then you're pulling on the rope as well?

And is this 'perceived gravity' due to what's called centrifugal force? How does it work and why does it make you feel as though gravity's pulling on you? Doesn't the centripetal force point inwards?
 
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  • #2
Compare holding on a rope hanging in strong gravity to holding on a rope being swung around a pivot. In the first case, you and the rope must supply a force to keep you from falling down. Your grip on the rope has to hold your weight, so you are pulling yourself upwards to counteract gravity which is pulling you down. The rope is also pulling you up. In the second case, you and the rope must supply a force to keep pulling you inward, toward the pivot. But you feel a fictitious force, centrifugal force, pulling you outward from the pivot, so you must pull on the rope to keep yourself on the rope.

Centripetal force points inward. You and the rope supply the centripetal force.

In an inertial frame of reference, centrifugal force doesn't exist, and centripetal force points inward, pulling you in a circle. In a rotating frame of reference, centrifugal force points outward, and centripetal force points inward, canceling out the forces on your body, so you don't move (relative to the rotating frame).
 
  • #3
Khashishi said:
Compare holding on a rope hanging in strong gravity to holding on a rope being swung around a pivot. In the first case, you and the rope must supply a force to keep you from falling down. Your grip on the rope has to hold your weight, so you are pulling yourself upwards to counteract gravity which is pulling you down. The rope is also pulling you up. In the second case, you and the rope must supply a force to keep pulling you inward, toward the pivot. But you feel a fictitious force, centrifugal force, pulling you outward from the pivot, so you must pull on the rope to keep yourself on the rope.

Why do ou feel the force pulling you outward?
 
  • #4
Without any forces, you would move in a straight line, which would take you away from the pivot. Thus, inertia is the source of this centrifugal force. You have to fight inertia to stay a fixed distance from the pivot, hence it feels like a force is pulling you away.
 
  • #5
Ok...let's see if I understand this...

Say you're on some sort of giant turntable with a wall. If the friction between the floor and you isn't enough to provide the centripetal force to keep you turning with the turntable, then you slide and hit the wall. Now the wall is pushing against you to provide the centripetal acceleration, and the reaction force of you against the wall is the force you feel - the 'artificial gravity'? Is that right?

And for the ball and the rope, the rope pulls on the rope and so the reaction force in the non-inertial frame is the ball pulling back on the rope, and it's this pulling is the gravity that the ball feels

Also, in the non-intertial frame, you don't think you are accelerating do you? You just feel a force pushing you outwards if the friction between you and the floor isn't enough to keep you going in a circle
 

Related to Centrifugal force and artificial gravity

1. What is centrifugal force?

Centrifugal force is the outward force acting on an object that is rotating around a center point. It is caused by the inertia of the object trying to continue in a straight line even as it is forced to move in a circular path.

2. How does centrifugal force create artificial gravity?

Centrifugal force can create the feeling of artificial gravity by pulling objects towards the outer edge of a rotating object. This creates a sense of downward force that mimics the effects of gravity.

3. What is the relationship between centrifugal force and rotation speed?

The strength of centrifugal force is directly proportional to the speed of rotation. This means that the faster an object rotates, the stronger the centrifugal force will be.

4. Can centrifugal force be used to create artificial gravity in space?

Yes, centrifugal force can be used to create artificial gravity in space. This is often done by rotating a spacecraft or space station to create the feeling of gravity for astronauts on board.

5. Are there any limitations to using centrifugal force for artificial gravity?

One limitation of using centrifugal force for artificial gravity is that it only works in a circular motion. This means that objects near the center of rotation may experience less artificial gravity than those near the outer edge. Additionally, the size and speed of the rotating object would need to be carefully calculated to create the desired amount of artificial gravity without causing discomfort for those on board.

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