Question

in centripetal force the acceleration is said to be towards the center of the circle...why is it that the visible force is always pushing in the oppisite direction...i.e. a lettuce dryer or washing machine...is it an intangible force...the only time i can imagine it is when i think of an object on a string being whirled around...in the washing machine case is it the force exerted by the machine to keep the clothes from pushing through the metal drum?

Answer 1

There are two forces at play here...centripetal and centrifugal.

Here's a decent explanation of each and how they are related which should help you:

http://www.infoplease.com/ce6/sci/A0811114.html

Answer 2

first of all there is no such thing as a centrifugal force. my college physics professor told me he would "shoot you" if you said centrifugal force. there is a force associated with a centripetal acceleration \[F = \sum_{}^{}m*a\] where a is the centripetal accerleration.
Newtons 3rd law of motion state that for every action there is an equal and opposite reaction... a static translation: for every force there is a force of the same magnitude in the opposite direction.

Answer 3

I can agree that centrifugal force is not a true force...but you can't deny that there is a force that opposes centripetal acceleration. Centrifugal is just a common name for it.

Answer 4

Centrifugal force is a psudo force

Answer 5

The visible force that you're talking about is, as stated above, the centrifugal force or a pseudo force.
the best example that got this concept cleared to me is that of a passenger in a train. Suppose, initially, you're on the train and the train is moving in a straight line (case A). Now it takes a left turn along a curve (case B). I'll try to draw it out for you. Consider the curve to be an arc of a biiiig circle. So this part can be considered as circular motion and our centripetal force comes into play. Now, the 'you' on the train will experience an outward push towards right. when you're on the train, moving linearly, there is actually no force being acted on you. So, in the train's frame of reference, you're at rest. But to a by-stander outside the train, you appear to be in motion along with the train. When the train takes the turn, centripetal force is applied on the the train and NOT on you. In the absence of that force, you try to maintain your state of rest (on train)/ of linear motion (as seen by a by-stander). In B, the dotted line shows the linear path you should've taken, had the train gone straight. As you can see, that outward push you felt when the train took the turn, is actually your own inertia (Newton's 1st law). This means that NO force is being applied for you to feel that push. This is of course, from a by-stander's frame of reference. But if you would ask a fellow passenger to explain why you're being pushed outward, he would not be able to answer. Because his frame of reference (ie, the train) is accelerated. and Newton's laws are not applicable to accelerated frame of reference.
So to help that poor fellow passenger answer you question, the concept of pseudo force was developed. It is an imaginary force which enables us to still use Newton's laws and equations even in an accelerated frame of ref.
Now, when our accelerated frame of ref is undergoing circular motion, the pseudo force we use is called centrifugal force.