Eli5 Centripetal force vs centrifugal force.

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Hi, i am having trouble understanding why centrifugal force is a “psuedo” force. Centripetal force holds an object in rotation pulling toward the centre , whereas centrifugal force is pushing the object outwards.

I have veen trying to watch videos but the examples dont really help.

For example, if im in a car going around a corner, the faster i go, the more the car wants to fly off the road.

Or if an object us on a spinning platform like a lazy susan, the faster i spin the lazy susan, the further away the object gets (until it falls off).

Is centrifugal force just the lack of centripetal force?

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8 Answers

Anonymous 0 Comments

It’s a useful way for folks to think about issues in an accelerating frame of reference. It’s not a real force because it’s just inertia. The diagram or thought model you should use is:

Does a body pass through my hand?

If it does, I’m pushing it inward and forcing it to curve. This is actually common in low-g (microgravity) scenarios, where an astronaut can just give an object a good push to keep it moving in a circle. This is actually how orbit raising for the ISS works – a big rocket, known as a Service Module, has to boost the orbit of the combined vehicle out of the atmosphere periodically since there’s just enough drag up there to accumulate over time and cause the ISS to fall out of its low, low orbit and begin deorbiting (which is no bueno).

Remember the basic definition of force: f = ma. If an object is in a circle, the force we’re talking about is the inward, radially directed force (centripetal). If you miss this force by missing your object or somehow don’t apply it, the object will not move in a circle. It will cease to be in an orbit – it will continue on its straight-line trajectory that would happen when no forces are acting upon it. This is basic Newtonian physics.

But sometimes, even physicists and engineers tend to personify these forces, which isn’t entirely accurate, but it does make for easier conversation. We say that, if an object is in a circle, there must be an inward, radially directed force pointing towards the center (centripetal force). This force, however, is not acting upon the object itself, but is actually the *result* of the object moving in a circle. If the object started to move in a linear path tangent to the circle, there’d be a noticeable push of the object outward from the center of the circle. This is actually the centrifugal force, but it’s not a good, intuitive way to think of the problem since it doesn’t actually exist. Again, there’s no force pushing on the object outwardly, but it’s just another way of trying to express the object’s reticence to deviate from its current path.

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