Centripetal vs centrifugal acceleration

In summary, the conversation discusses the difference between centripetal and centrifugal forces and how they relate to problems involving circular motion. The centripetal force is an actual force that keeps objects in circular motion while the centrifugal force is a fictitious force that appears to push objects away from the center. The conversation also touches on the concept of inertial frames and how they affect the experience of forces. The conversation ends with a discussion on setting up a problem involving friction and centripetal force to find the minimum rotational speed to prevent falling in a spinning carnival ride.
  • #1
dnt
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i don't quite understand the difference between the two. i know centripetal means towards the middle and centrifugal goes out but i can't quite relate that to the problems.

for example, if you are twirling a ball on a string above your head in a circle, the centripetal acceleration points towards the middle and acts on the ball? but where is the centripetal acceleration? how does that figure into it?

are they just opposite forces?

in a related problem, its dealing with those spinning carnival rides where the floor drops from below you but you don't fall due to centripetal forces.

now the question says the coefficient of friction is .30 and the radius is 2.5 m, whatis the minimum rotational speed so you don't fall...this is what i have so far:

looking at a person on the ride, you have gravity (mg) down and friction upward. to make sure he doesn't fall you set the two forces equal to each other. now the friction is equal to the 0.30 times the normal force, which i believe in this case is the force due to centripetal acceleration (pushing the guy against the wall)? is that right (or is it centrifugal?) that equals mv^2/r.

so if i set mg = mv^2/r and the m's cancel out, i can solve for v. then i can convert that into a rotational speed? is my work correct?

thanks.
 
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  • #2
The centripetal force is the force responsible for the maintenance of circular motion. So it's an actual force acting on the object and of course directed towards the center (centripetal=centre-seeking)

From the point of view of an object in circular motion, it seems as though there is a force which wants to pull it away from the center. This is called the centrifugal force. It is a ficticious force, so in reality not really a force at all. When we place ourselves in a noninertial frame there are all kinds of ficticious forces. Like on earth, because it spins it is not an inertial frame. We experience a centrifugal force, but also coriolis forces etc.

You know when a car accelerates you get pushed back into your seat? That's also a ficticious force. Nothing is pushing you backwards, rather, the seat is pushing you forward. The apparent force is ofcourse equal and opposite the real one. So also is the centrifugal force equal and opposite the actual centripetal force.
 
  • #3
thanks - did i set up my problem correctly?
 
  • #4
Friction = mu*Normal Reaction
and
Friction = mg
so
mg = mu*mv²/r

Other than that, your analysis of what's happening is absolutely correct
 

What is the difference between centripetal and centrifugal acceleration?

Centripetal acceleration is the acceleration directed towards the center of a circular path, while centrifugal acceleration is the outward acceleration away from the center of a circular path.

Which direction do centripetal and centrifugal acceleration act?

Centripetal acceleration acts towards the center of a circular path, while centrifugal acceleration acts away from the center of a circular path.

Are centripetal and centrifugal acceleration equal in magnitude?

No, they are not equal in magnitude. Centripetal acceleration is always greater in magnitude than centrifugal acceleration.

What is the relationship between centripetal and centrifugal acceleration?

The two accelerations are equal in magnitude but opposite in direction.

How do centripetal and centrifugal acceleration affect an object's motion?

Centripetal acceleration causes an object to move in a circular path, while centrifugal acceleration tends to make the object move away from the center of the circle.

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