Why is Centrifugal force “not real”? I remember my physics teacher in high school pushing that idea and understanding why back then, but I do not remember now. I also forgot so much about physics in general that a simple would be much appreciated!
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Consider a particle spun around and around in circles on a string in the horizontal plane.
You can get this effect by spinning a fully extended yoyo in circles.
The particle/yoyo continually changes direction and therefore Is accelerated and therefore has a external resultant force.
This force is the tension in the string. It is called the centripetal force. It is the ‘real’ force of the string pulling on the particle.
Now imagine you are an ant clinging of for dear life on the yoyo. You will feel an apparent force lifting you away from the rotation of the yoyo. In this frame of reference It is not a real force because it is only the effect of the yoyo pulling in whilst the ant is going in a straight line tangent to the motion of the yoyo. Even though the ant ‘feels’ it, there is no actual magical force godlike force pulling the ant away from the surface of the yoyo.
most physics is done in “inertial reference frames”, which basically means from the point of view of someone who’s moving at constant speed and not rotating. In an inertial reference frame, if you look at, say, a ball at the end of a rope that someone is spinning in a circle, there is no force moving outwards. The ball is moving exactly the way you’d expect if the only force on it is the tension of the rope, and that’s usually exactly how the situation is described.
It’s only when you look at that system from a reference frame that’s spinning along with it, for instance from the point of view of the person holding the rope and spinning, that there seems to be a centrifugal force. If they looked to their side at the ball as they spun, they would see the ball staying still in their vision. Since the rope is pulling the ball inward, there must be another force pulling outward to keep the ball “in place”, and that’s called “centrifugal force”
Since centrifugal force only really appears if you’re doing physics in a strange way (non-inertial reference frame), it’s considered a fictitious force. However, spinning reference frames come up often enough that it’s still often a useful concept.
Consider a particle spun around and around in circles on a string in the horizontal plane.
You can get this effect by spinning a fully extended yoyo in circles.
The particle/yoyo continually changes direction and therefore Is accelerated and therefore has a external resultant force.
This force is the tension in the string. It is called the centripetal force. It is the ‘real’ force of the string pulling on the particle.
Now imagine you are an ant clinging of for dear life on the yoyo. You will feel an apparent force lifting you away from the rotation of the yoyo. In this frame of reference It is not a real force because it is only the effect of the yoyo pulling in whilst the ant is going in a straight line tangent to the motion of the yoyo. Even though the ant ‘feels’ it, there is no actual magical force godlike force pulling the ant away from the surface of the yoyo.
most physics is done in “inertial reference frames”, which basically means from the point of view of someone who’s moving at constant speed and not rotating. In an inertial reference frame, if you look at, say, a ball at the end of a rope that someone is spinning in a circle, there is no force moving outwards. The ball is moving exactly the way you’d expect if the only force on it is the tension of the rope, and that’s usually exactly how the situation is described.
It’s only when you look at that system from a reference frame that’s spinning along with it, for instance from the point of view of the person holding the rope and spinning, that there seems to be a centrifugal force. If they looked to their side at the ball as they spun, they would see the ball staying still in their vision. Since the rope is pulling the ball inward, there must be another force pulling outward to keep the ball “in place”, and that’s called “centrifugal force”
Since centrifugal force only really appears if you’re doing physics in a strange way (non-inertial reference frame), it’s considered a fictitious force. However, spinning reference frames come up often enough that it’s still often a useful concept.
It’s a fictitious force, so it’s only used in a non intertial reference frame. Now what does that mean?
A non intertial reference frame means that the frame of reference you are measuring the motion against, is accelerating.
An example of an intertial reference frame would be what you do in conventional physics. The ground is stationary, and if you throw a ball, it acts exactly as you’d expect.
Another example of an inertial reference frame would be a car moving at a constant velocity. You throw the ball and it travels exactly the same as before.
Once you start accelerating the car, the reference frame becomes non inertials. Let’s say the car is accelerating at “a”. If you throw the ball now, it will appear to be accelerating the opposite direction of the car, so to be in the reference frame of the car, we need to add a fictitious force acting on the ball such that F=ma, m being the mass of the ball, a being the acceleration of the car. When you get pressed back into the seat of the accelerating car, or get thrown forward by a fast stop, that’s the same fictitious force.
The centrifugal force is for a rotating reference frame. Since the centripetal force is constantly accelerating everything in the rotating body towards the center, if we want to be in the reference frame of the rotating body we need a ficticious force acting outward on everything in the system. We call this force the centrifugal force and it will have an equal magnitude and opposite direction of the centripetal force that would allow the object to travel in circular motion.
Another fictitious force for rotating reference frames is the coriolis force, you may have heard of the coriolis effect, the coriolis force is how we explain it while keeping the Earth as the reference frame. This one only applies when the object in the reference frame moves towards or away from the axis of rotation.
Consider a particle spun around and around in circles on a string in the horizontal plane.
You can get this effect by spinning a fully extended yoyo in circles.
The particle/yoyo continually changes direction and therefore Is accelerated and therefore has a external resultant force.
This force is the tension in the string. It is called the centripetal force. It is the ‘real’ force of the string pulling on the particle.
Now imagine you are an ant clinging of for dear life on the yoyo. You will feel an apparent force lifting you away from the rotation of the yoyo. In this frame of reference It is not a real force because it is only the effect of the yoyo pulling in whilst the ant is going in a straight line tangent to the motion of the yoyo. Even though the ant ‘feels’ it, there is no actual magical force godlike force pulling the ant away from the surface of the yoyo.
most physics is done in “inertial reference frames”, which basically means from the point of view of someone who’s moving at constant speed and not rotating. In an inertial reference frame, if you look at, say, a ball at the end of a rope that someone is spinning in a circle, there is no force moving outwards. The ball is moving exactly the way you’d expect if the only force on it is the tension of the rope, and that’s usually exactly how the situation is described.
It’s only when you look at that system from a reference frame that’s spinning along with it, for instance from the point of view of the person holding the rope and spinning, that there seems to be a centrifugal force. If they looked to their side at the ball as they spun, they would see the ball staying still in their vision. Since the rope is pulling the ball inward, there must be another force pulling outward to keep the ball “in place”, and that’s called “centrifugal force”
Since centrifugal force only really appears if you’re doing physics in a strange way (non-inertial reference frame), it’s considered a fictitious force. However, spinning reference frames come up often enough that it’s still often a useful concept.
It’s a fictitious force, so it’s only used in a non intertial reference frame. Now what does that mean?
A non intertial reference frame means that the frame of reference you are measuring the motion against, is accelerating.
An example of an intertial reference frame would be what you do in conventional physics. The ground is stationary, and if you throw a ball, it acts exactly as you’d expect.
Another example of an inertial reference frame would be a car moving at a constant velocity. You throw the ball and it travels exactly the same as before.
Once you start accelerating the car, the reference frame becomes non inertials. Let’s say the car is accelerating at “a”. If you throw the ball now, it will appear to be accelerating the opposite direction of the car, so to be in the reference frame of the car, we need to add a fictitious force acting on the ball such that F=ma, m being the mass of the ball, a being the acceleration of the car. When you get pressed back into the seat of the accelerating car, or get thrown forward by a fast stop, that’s the same fictitious force.
The centrifugal force is for a rotating reference frame. Since the centripetal force is constantly accelerating everything in the rotating body towards the center, if we want to be in the reference frame of the rotating body we need a ficticious force acting outward on everything in the system. We call this force the centrifugal force and it will have an equal magnitude and opposite direction of the centripetal force that would allow the object to travel in circular motion.
Another fictitious force for rotating reference frames is the coriolis force, you may have heard of the coriolis effect, the coriolis force is how we explain it while keeping the Earth as the reference frame. This one only applies when the object in the reference frame moves towards or away from the axis of rotation.
Isn’t what we refer to as centrifugal force actually centripetal acceleration?
It’s a fictitious force, so it’s only used in a non intertial reference frame. Now what does that mean?
A non intertial reference frame means that the frame of reference you are measuring the motion against, is accelerating.
An example of an intertial reference frame would be what you do in conventional physics. The ground is stationary, and if you throw a ball, it acts exactly as you’d expect.
Another example of an inertial reference frame would be a car moving at a constant velocity. You throw the ball and it travels exactly the same as before.
Once you start accelerating the car, the reference frame becomes non inertials. Let’s say the car is accelerating at “a”. If you throw the ball now, it will appear to be accelerating the opposite direction of the car, so to be in the reference frame of the car, we need to add a fictitious force acting on the ball such that F=ma, m being the mass of the ball, a being the acceleration of the car. When you get pressed back into the seat of the accelerating car, or get thrown forward by a fast stop, that’s the same fictitious force.
The centrifugal force is for a rotating reference frame. Since the centripetal force is constantly accelerating everything in the rotating body towards the center, if we want to be in the reference frame of the rotating body we need a ficticious force acting outward on everything in the system. We call this force the centrifugal force and it will have an equal magnitude and opposite direction of the centripetal force that would allow the object to travel in circular motion.
Another fictitious force for rotating reference frames is the coriolis force, you may have heard of the coriolis effect, the coriolis force is how we explain it while keeping the Earth as the reference frame. This one only applies when the object in the reference frame moves towards or away from the axis of rotation.
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