Question about Centripetal force

In summary, centrifugal force is a fictitious force that appears when viewing things from a rotating frame of reference. Centripetal force is the real force that creates tension on the string.
  • #1
nuby
336
0
If a string is attached to a weight and swung around overhead, is the force that creates tension on the string centripetal, centrifugal, or both?
 
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  • #2
What do you think?
 
  • #3
nuby said:
If a string is attached to a weight and swung around overhead, is the force that creates tension on the string centripetal, centrifugal, or both?

Centripetal. Centrifugal force can only be measured in a rotating frame of reference.

Pete
 
  • #4
I think centripetal would always exist in the string. But, centrifugal (reactive) force would depend on the rigidity of the string.
 
  • #5
nuby said:
I think centripetal would always exist in the string. But, centrifugal (reactive) force would depend on the rigidity of the string.
Still insist on using that archaic meaning of centrifugal force as the "reaction" force to centripetal force? If so, then it's simple: The string pulls the object (centripetal) and the object pulls the string ("centrifugal"). Can't have one without the other.

One more time though: This is an old-fashioned usage of the term centrifugal. The modern usage is as a "fictitious" force that appears when viewing things from a rotating frame of reference.
 
  • #6
Doc Al said:
Still insist on using that archaic meaning of centrifugal force as the "reaction" force to centripetal force? If so, then it's simple: The string pulls the object (centripetal) and the object pulls the string ("centrifugal"). Can't have one without the other.

One more time though: This is an old-fashioned usage of the term centrifugal. The modern usage is as a "fictitious" force that appears when viewing things from a rotating frame of reference.

Just to add to what Doc Al said, the concept of "force" is actually a very slippery one. Technically, a force is the rate of change of momentum away from what the natural trajectory would have been. In other words, it doesn't really make sense to talk about a force without fixing trajectories first. Normally, in an inertia frame, things move in straight lines (ignoring gravity). So if something moves in a circle, there must be a force to make it do so --- we call that "centripetal". However, if we're in a rotating frame, things tend to move away from the centre, so if something doesn't then you need a force --- we call that one "centrifugal".
 
  • #7
Doc Al said:
Still insist on using that archaic meaning of centrifugal force as the "reaction" force to centripetal force? If so, then it's simple: The string pulls the object (centripetal) and the object pulls the string ("centrifugal"). Can't have one without the other.
archaic? Was it true? For the example which nuby explain,
a string is attached to a weight and swung around overhead
What are the action-reaction forces? Say the one is centripetal force, what is the other?
 
  • #8
The "action/reaction" pair is: String pulls on object & object pulls on string. When considering the motion of the object, we call the first force the centripetal force. The second force has no particular name. (Some folks call that second force the "centrifugal" force--but that's nonstandard usage. Old-fashioned and out of date!)
 
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  • #9
Doc Al said:
The "action/reaction" pair is: String pulls on object & object pulls on string. When considering the motion of the string, we call the first force the centripetal force. The second force has no particular name. (Some folks call that second force the "centrifugal" force--but that's nonstandard usage. Old-fashioned and out of date!)
I thought the second one was inertia - the object's tendency to continue moving in a straight line.
 
  • #10
Inertia is not a force.
 
  • #11
Ok. centripetal-centrifugal forces pair never action-reaction forces.

Other hand, for this example, I suppose the pair of centripetal force is a force like so; say we pull a body by means of a string in space. There is no other force(friction, weight) then we apply. But anyway string will have has a tension. If this true, this is inertia force. But it is a pair-less fictitious force. Then how will we call it? :-/
 
  • #12
Net force?
 
  • #13
The string "pulls" on the body and the body "pulls" on the string, this forms a force-reaction pair. Equally, we "pull" on the string and the string "pulls" on us, again a force-reaction pair.

What is this fictitious force your talking about?
 
  • #14
Volcano said:
Other hand, for this example, I suppose the pair of centripetal force is a force like so; say we pull a body by means of a string in space. There is no other force(friction, weight) then we apply. But anyway string will have has a tension. If this true, this is inertia force. But it is a pair-less fictitious force. Then how will we call it? :-/
As Hootenanny already explained, the string pulls on the object and the object pulls on the string. Two very real forces--nothing "fictitious" here.
 
  • #15
Is it possible centrifugal force doesn't exist in the string at all? If you take the ball way and spin the string around by itself, the string would probably just get tangled around the axis. Would there be any centrifugal force in this example?

Maybe the string only transfers force to the weight? i.e. Weight pulls on spinning axis through string, and the rigidity of the string controls the rate force is transfered.
 
  • #16
nuby said:
Is it possible centrifugal force doesn't exist in the string at all?
According to your nonstandard definition of "centrifugal" force: NO. The string can't pull without being pulled.
 
  • #17
Hootenanny said:
What is this fictitious force your talking about?
I tried to understand second force on weight which asked in first post. Doc_Al said has no particular name and DaveC426913 said inertia. You and Doc_Al are right. I must be mad. Don't know how and why confused so much. Ok.
 
  • #18
centrifugal force is a misnomer. what people refer to as centrifugal force is actually centrepetal force to the best of my knowledge.
 
  • #19
patrickdt10 said:
centrifugal force is a misnomer. what people refer to as centrifugal force is actually centrepetal force to the best of my knowledge.
No, centripetal force is the force pulling inward. Centrigual force is plain-old garden variety inertia as seen from the rotating reference frame. (i.e. if the string tied to the rotating bucket of water were to break, the bucket would continue in a straight line tangential to the bucket's former circular path).
 

What is centripetal force?

Centripetal force is a force that acts on an object moving in a circular path, directed towards the center of the circle. It is responsible for keeping the object moving in a curved path instead of a straight line.

What is the formula for calculating centripetal force?

The formula for calculating centripetal force is F = mv^2/r, where F is the force, m is the mass of the object, v is the velocity, and r is the radius of the circular path.

What are some real-life examples of centripetal force?

Some real-life examples of centripetal force include the rotation of a Ferris wheel, the movement of a car around a circular track, and the orbit of planets around the sun.

Can centripetal force be greater than the weight of an object?

Yes, centripetal force can be greater than the weight of an object. This occurs when the object is moving at a high speed or has a smaller radius of circular motion, resulting in a larger centripetal force.

How is centripetal force related to centripetal acceleration?

Centripetal force and centripetal acceleration are directly related. Centripetal acceleration is the acceleration of an object moving in a circular path, and it is equal to v^2/r, where v is the velocity and r is the radius. This is also the same as the formula for centripetal force, demonstrating their close relationship.

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