The Myth of Centrifugal Force

We all know that centrifugal force exists don’t we?   It’s the outward force on an object traveling in a circle.  Pretty hard to deny it exists when we’ve all felt it every time we go around a tight turn in a car.

Except it really doesn’t exist, and you can prove it to yourself.  Take a small object and tie a string to it.  Then swing it in a circle (hey if you’re actually going to do this don’t go berserk and hurt someone or yourself).  Now that you have the object swinging around in a circle, ask yourself this question; are you pushing on the string or pulling on it?  You are pulling on it of course, you can’t push something around through a string.  What happens when you suddenly let go (safety precautions again of course, and if you break a window or hit someone I am not responsible).  As soon as you stop pulling on the string (applying an inward, not outward force) the object will fly off in a straight line.  No more force inward, no more going in a circle.

But the fact is it feels like there is an outward force when the car goes around a tight corner.  What is actually happening is that your body has momentum and is trying to go in a straight line.  What you are feeling is your momentum as the car starts to move sideways underneath you.  You’re not being thrown up against the side of the car.  The side of the car is moving over and pushing on you to make you go in a circle too.  The force it applies is called centripetal force.

23 Responses to The Myth of Centrifugal Force

  1. MMaDave says:

    Many thanks for sharing this great advice here.

  2. I agree, it’s I like, probably in the future …

  3. I never thought of it that way, well put!

  4. Pingback: cercueil

  5. Anne Dransfield says:

    Why don’t you send this to Wikipedia!

  6. Starski says:

    The spinning action of the ball will not keep spinning if you let go of the string, thats not centifugal force. Its the spinning action of the ball from a stand still, that moves the ball up towards the sky perpendicular to your hand that is doing the spinning, would be the centrifugal force! The ball out weighs the string, so of course it will not keep spinning, look at an Australian Boomer Rang it has equal weight on either side so it will spin!

    • davidmhoffer says:

      The two don’t equate. The boomerang spins about itz centre of gravity. The weight going around in a circle attached to the end of a string is circling the point at which the string is held down. You can swing it in the horizontal plane, or the vertical plane, or anything in between, but the moment that you let go that string (thus removing the force pulling the weight to the centre of the circle) the weight simply travels off in a straight line tangential to the circle. Force having been removed, the weight travels in a straight line. What was the force in the first place? When you were swinging the weight around in a circle, were you pushing on it (centrifugal) or pulling on it (centripetal)?

  7. Thane Fowl says:

    SIMPLY CONSTRUCT NEWTONS LAWS IN A ROTATING SYSTEM AND YOU WILL SEE A CENTRIFUGAL FORCE TERM APPEAR AS PLAIN AS DAY. To transform equations to a subsystem, everything inherent to the system as a whole must be subtracted, including the centripetal forces, which leaves a centrifugal force on the other side of the equation. While the centripetal force is universal, the centrifugal force is bound to the specific inertial system.

  8. Adrian says:

    I cannot believe that folk are actually arguing this common sense. The constructs they put together in argument is mind blowing and a direct analogy to the arguments one encounters against atheism.
    If anyone ever argues this with me in person, I will slap him and claim/blame centrifugal force on his part.

    • Adrian says:

      I cannot believe that folk are actually arguing this common sense. The constructs they put together in argument is mind blowing and a direct analogy to the arguments one encounters against atheism.
      If anyone ever argues this with me in person, I will slap him and claim/blame centrifugal force on his part.

  9. geoff says:

    Centrifugal force can be understood by a simple experiment; if one considers a mechanical system where, both a central pivot and a body tethered adjacent, move at the same velocity in the same direction, with no shortening of the tether, then there is no centripetal force or centrifugal force and no change in direction. If the central pivot point is stoped, the tethered body will start to change direction to a circular orbit and express centripetal force.
    What has happened is that the orbiting body is attempting to advance ahead of the central pivot to get beyond right angles. In doing this it attempts to exceed the length of the tether and in doing this is pulled constantly slightly backwards since the tether is a constant length. This is the application of an external force, and this must retard angular momentum. Since angular momentum is a constant without retardation, there must be an external force being applied in the opposite direction to the centripetal force to offset that centripetal force. Such a force is called centrifugal force however it is caused.
    If an orbiting body such as the moon was to be stationary within the principle influence of the earth’s gravity, it would be pulled directly toward the earth at an accelerating velocity until it crashed into the earth. In the natural world the moon does not crash into the earth because it is orbiting at a constant velocity that produces centrifugal force at its radius from the earth that balances the earth’s gravity.
    Centrifugal force is used in the centrifuge by amplifying mass for separation. It is used in the speed governor by mechanically applying the revolution rate to the outward pull of centrifugal force. It is used by the rotary lawn mower to hold the pivoted blades fully outwards despite the resistance of the grass cutting. It is used by the centrifugal clutch where brake pads are spun, and so forced out against the inner face of a drum with a force that creates friction to lock the inner rotation to the outer drum.
    See web site —

    • davidmhoffer says:

      Sorry, but you have an awful lot of basic physics simply wrong. If you understand orbital mechanics, the moon (or anything else in orbit) is actually falling, all the time. The earth being round, if the moon were to travel in a straight line, it would be increasingly higher than the earth surface. But if falls due to the force of gravity. The amount if falls exactly equals the change in height that would otherwise have occurred, resulting in the moon being the same distance all the time. This is where the term “free fall” is derived from. There is no other force than gravity, which is toward the centre of the system.

      The rest of your explanation is similarly flawed.

    • dcardno says:

      All that, and a link to a site promoting what seems to be a perpetual motion device.
      You just can’t make this stuff up!

  10. Frank Smith says:

    “We all know that centrifugal force exists don’t we? It’s the outward force on an object traveling in a circle. Pretty hard to deny it exists when we’ve all felt it every time we go around a tight turn in a car.”
    No It’s not, it’s the outward force “Exerted” by an object travelling in a circle on the restraining mass; any decent book on physics will confirm this.

  11. Frank Smith says:

    David M Hoffer, in his reply dated 9/10/2014 is correct in stating objects don’t travel in a circle unless a force is exerted on them, there are, however, two forces involved. If you swing a ball on a piece of string your hand will exert a centripetal force on the ball, the ball in its turn will exert an equal and opposite centrifugal force on your hand. This obeys Newton’s third law “For every action there is an equal and opposite reaction.” Once again any decent book on physics will confirm this.

  12. Vihar Gandhi says:

    actually it can be

  13. Very Equipped says:

    This thesis PROVES centrifugal force. Do the experiment as noted, then stop moving your arm and let the object pivot around your arm, and while it’s doing that let go. It’ll fly. This is proof there is an outwords force. This argument only tries to debate the directional force of the object after release. Try placing a small object on a record player and turn the spin on. what happens to that object? That’s called centrifugal force.

    • davidmhoffer says:

      When you let go, it does indeed fly. IN A STRAIGHT LINE! No force being exerted, STRAIGHT LINE!

      The record player is a rather more complex example, but is the same thing. Friction is keeps the small object going in a circle. When/if the rotational speed of the object requires more centripetal force than friction can sustain, the object starts to slide in a straight line, but in fits and starts which break up the motion giving it an over all motion comprised of movements tangential to a changing position. Bottom line though, is the LACK of enough friction to keep the object rotating in a circle is why it skitters off. Take your own example, but use something sticky like a piece of tape or chewing gum. Because these things are sticky, there’s enough force to keep them going in a circle. Less sticky things skitter off because there is NOT enough force to keep them going in a circle.

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