I am a university educated (primarily sciences), middle aged dude and I still cannot understand the difference between these 2 forces / phenomena.
In: Physics
Centripetal force is a real force, while centrifugal force is an apparent force.
Newton’s first law states “a body remains at rest, or in motion at a constant speed in a straight line, except insofar as it is acted upon by a force.” So for something to move in a circle, there must be force pushing it towards the center of the circle. That is the centripetal force. Latin for “center seeking”.
For a yoyo being swung around, the force is the string pulling on it. For the planets and moons orbits, the force is gravity. For a car going around a curve, the force is the friction between the tires and the road.
But when you’re *in* the car, it certainly feels like you’re being swung outward and into the side. That’s the centrifugal force. Latin for “center fleeing”. It’s not a “real” force. In reality, your body is trying to stay on that straight line but the car is pushing you inward towards the center.
But within the reference frame of “inside the car”, objects are moving towards one side of the car. Even though centrifugal force isn’t real, it’s still useful for discussing what’s going on within that reference frame.
Centrifugal force is a fictitious for that seems to “press” matter against the wall of the centrifuge. Like have gravity presses your body to the ground. But it’s fictitious, it’s not real, it is simple motion and your bodies inertia that is making it SEEM like a force pushing you against the wall of those carnival rides. But when the ride stops, the “force” goes away. If the earth stopped spinning, gravity wouldn’t go away.
“Centripetal force” is a generic term that can actually apply to many different forces. Centripetal force is any force that pushing you towards the center of a circle/radius/curve. This could gravity, like where gravity acts as a centripetal force pulling the moon around the earth. This could be a “normal” force. Like in that carnival ride, the force of the wall of the carnival ride pushing against your body is a real force, that’s a centripetal force.
So to put it in carnival ride terms. Centrifugal force is a perceived force that pushes you AWAY from the center of a circle/curve. Centripetal force is a real force that causes you to circle/curve. Centrifugal force is your brain thinking you’re getting pushed against the wall. Centripetal force is the wall actually pushing against you (and keeping you from flying off the ride).
Centrifugal force is the fictitious force caused by an object’s inertia. Objects in motion want to stay in motion in a straight line. When you spin something, you’re constantly making it curve away from the straight line. The inertia that’s trying to keep it going in that straight line is centrifugal force.
The path the object actually takes is a circle. The path inertia is trying to make it take is a straight line. [So, the inertial path is a tangent to the circle.](https://d138zd1ktt9iqe.cloudfront.net/media/seo_landing_files/prove-that-perpendicular-at-point-of-contact-to-tangent-to-a-circle-pass-01-1625468278.png) To make it go in a circle, you are constantly accelerating it towards the center of the circle. The apparent force caused by inertia is opposite to that, which means it’s directly *away* from the center, 90° to the tangent, or “down” from your perspective with the center of the circle being “up.”
Centripetal force is the very real force that’s causing it to go in a circle instead of in a straight line. Since the object’s inertia “wants” to go in a straight line, you must apply some kind of force to accelerate it away from that straight line. That force is centripetal force. If you’re spinning something attached to a string, the centripetal force is the intermolecular forces holding the string together. For a planet orbiting a star, it’s gravity.
So: object wants to go in a straight line. Centripetal force doesn’t let it. Centrifugal force is it trying to anyway.
dude centrifugal force is what pushes you out when you’re on a merry-go-round while centripetal force keeps you from flying off into space both are super important for spinning stuff and make rides way more fun
The literal definition difference, from the words themselves, is “toward center” versus “away from center”.
But in practice they’re exactly the same force, with the direction flipping depending on what you choose as your frame of reference.
Picture a car making a 90 degree turn on some street intersection, turning in a quarter circle arc around an imaginary center point.
If you lay out your math model as “the world is stationary while the car moves” then the force is centri**petal** force – a force to the side of the car aimed at that center point of the circular arc pulls the car around the circular path.
If you lay out your math model as “the car is stationary as the world moves past its windows” then the force is centri**fugal** force – a force pulling the car and the things in it (the people) toward the outside of the circle, away from its center.
They’re the same thing, but the direction “feels” different depending on if you are standing outside the car looking at it drive past versus if you are inside the car looking out at the world around you.
In most situations the simpler math happens when you set up the model with the world being stationary with the car moving through it, which is why when learning the physics of it you will encounter the term “centripetal” much more often.
tl;dr: a centri*petal* force is the total force required to make something travel in a circle or curve, and points *towards* the centre of the curve.
The centri*fugal* force is a fictional force used when trying to model something in a situation where it and everything around it is going in a circle. Rather than treating its whole universe as accelerating inwards, we pretend there is some force pushing it outwards, and the maths all works out.
The centripetal force is what is going on when viewed from the outside. The centrifugal force is what you “feel” when on the inside.
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In more detail…
We have Newton’s 2nd Law, often written as *F = ma*.
This tells us that the *total* force on an object is equal to its acceleration, scaled by its mass. This has a few key consequences:
1. if something is accelerating, there must be some overall force acting on it,
2. if something isn’t accelerating (even if moving at some constant velocity), there must be no overall force acting on it (all the forces must be balanced),
3. if something has some overall force acting on it, it must be accelerating, and
4. if something has no overall force acting on it, it must be stay at the same velocity (kind of Newton’s First Law, ish).
We’re mostly going to be dealing with 1 here.
For something to be going in a circle, or curve, it must be accelerating. Acceleration is rate of change of velocity, velocity has a direction. If something is curving it is changing direction, so its velocity must be changing, so it must be accelerating, so there must be some overall force acting on it.
With a bit of geometry, that force must be pointing inwards, and we can work out its magnitude in terms of the speed and radius of curvature.
This is our centri*petal* force. It isn’t strictly speaking a force, but a *sum of forces* – it is the overall or total force needed to make our thing go in a circle (i.e. it is really the right-hand side of *F = ma*, a mass multiplied be a centripetal acceleration, not any one force on the left-hand side). “-petal” in this context comes from the Latin word for “seeking” or “aiming at”, (where we get words like compete, perpetual, repeat). If something is going in a circle the “centripetal force” tells you what overall force must be acting on that thing.
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But that’s not what *we* feel if we are the object moving in a circle. If you’ve ever been in a car going around a corner too fast, you *feel* pushed to the outside, not pulled inwards. What is happening in that case is that you are trying to keep going forwards (Newton’s First Law), but your local “universe” (the car you are in) is accelerating inwards (to go around the corner). Because your local universe is accelerating inwards, and you are trying to go straight, within your local universe you seem to be pushed outwards.
The centri*fugal* force is this outwards push (“-fug-” being Latin for fleeing away from something). But it isn’t entirely real; nothing is actually pushing you outwards. You are really being pushed inwards (by the car). You only appear to be being pushed outwards because the universe you are in is accelerating inwards. So a centrifugal force is a way of modelling the fact that something is in an accelerating reference frame. Mathematically, what we do is take our Newton’s 2nd law:
> total F = m[centripetal acceleration]
and split off the bit of accelerating that our reference frame is doing (so going around in a circle), and move it to the other side:
> F – m[centripetal acceleration] = 0
And because of the maths the sign (so direction) changes. Rather than saying “we are accelerating inwards with our whole universe” we pretend we are being pushed outwards.
It turns out this can be really useful in some situations. We end up with a “fictional” or “pseudo-” force which is a correction to account for the fact that our entire co-ordinate system is accelerating.
Imagine a ball on a string. If you start spinning it the string gets taut and the ball spins in a circle around you with its radius being the length of the string. What we call centrifugal force is the force that gets the string taut, like it’s pulling outwards. It’s not a real force because there isn’t really a force acting on the ball that pushes it outwards and gets the string taut. Rather it’s just a result of inertia and being connected to the string that makes it seem like something is pushing the ball outwards but really the ball is just trying to go straight and the string is preventing it.
The centripetal force is the string itself. It’s whatever is preventing a spinning body from flying off tangentially along it’s direction of travel and instead pulls it towards the center, thus forcing it to trace a circular path rather than a straight one.
So centrifugal force is the force pushing outwards on a spinning body and the centripetal force is the force that pulls it inwards, what’s essentially making it spin instead of going straight.
so basically centripetal force pulls stuff towards the center like a friend pulling you in during a game of tug-o-war. centrifugal force is like the feeling you get when you’re spinning around and want to fly off into space. one is the force keeping you in check while the other is just your body’s reaction to the spin. kinda like when i try to keep my room clean but gravity is just like nah
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