Centrifugal force?
Poll: Centrifugal force?
Total Members Polled: 72
Discussion
Engineer1 said:
And that was my point about centrifugal force if it was pulling out then the moment the string went the bucket would accelerate away along the radius as the force preventing this had gone
No, that's wrong.Whilst it's still going in a circle, you've got the acceleration, and the force needed for the accel to happen.
When the rope breaks, the force creating the accel has gone, so no more accel, so it now continues at constant velocity, in the direction it was going in at the moment the rope broke, ie tangentially, not radially.
Engineer1 said:
I know. I answered this correctly earlier. but am saying if centrifugal force acted to push the item out rather than centripetal force acting in, then a failure of the string would see it fly off radially -the unbalance force would be radial.
It would help if you typed in your own punctuation marks. 
Tony2or4 said:
Most of what you say here is spot on, TS, apart from the bit about there being a reaction force balancing the centripetal force.
Because it's moving in a circle - ie moving with non-constant velocity (even if the speed is constant) - the bucket is undergoing an acceleration, and the only force needed for that to happen is the centripetal force (in the form of tension in the rope).
The reaction force (as in Newton's 3rd law) is the force experienced by the bloke in his arm.
Yes, I didn't word that particularly well. The reaction force is what people call centrifugal force. The person pulling on the string feels it as the bucket pulling outwards, but it doesn't exist unless the centripetal force is also present, so removing that by cutting the string immediately removes the centrifugal force as well. It's not a very intuitive thing to visualise!Because it's moving in a circle - ie moving with non-constant velocity (even if the speed is constant) - the bucket is undergoing an acceleration, and the only force needed for that to happen is the centripetal force (in the form of tension in the rope).
The reaction force (as in Newton's 3rd law) is the force experienced by the bloke in his arm.
Tony2or4 said:
Simpo Two said:
Perhaps if I'd been any good at maths once all the numbers turned into letters, I might be famous by now 
No you wouldn't. Maths was the only thing I was any good at and I'm still not famous.
ETA My being not famous is illustrated by the fact that when I googled my own name, the only thing that came up was a reference to me retiring in the school's online magazine.
You either need to invent antigravity (actually it's just normal gravity but inverted) or be a Brian Cox type of bod. I know a PR chap if it would help
Tony2or4 said:
Engineer1 said:
And that was my point about centrifugal force if it was pulling out then the moment the string went the bucket would accelerate away along the radius as the force preventing this had gone
No, that's wrong.Whilst it's still going in a circle, you've got the acceleration, and the force needed for the accel to happen.
When the rope breaks, the force creating the accel has gone, so no more accel, so it now continues at constant velocity, in the direction it was going in at the moment the rope broke, ie tangentially, not radially.
Engineer1 said:
...if centrifugal force acted to push the item out rather than centripetal force acting in then a failure of the string would see it fly off radially, the unbalance force would be radial
This is the central point of this thread, isn't it?The fact is that there is no force acting outwards on the bucket. The force on the bucket only ever acts inwards - that's the tension in the string - and as soon as the string breaks, there is no more force acting on the bucket, either inwards or outwards, so the bucket just does its Newton's 1st law thing, ie continues on in a straight line, tangentially.
Actually a good way to visualise what happens when the string breaks is to picture a hammer-thrower in athletics: when he lets go of the hammer ( = string breaking) the hammer goes off tangentially, not radially.
grumbledoak said:
^^^ You two are still in violent agreement. 
You need to re-read Engineer1's posts again as if he had punctuated them. Two or three times.
Never was there a more gentlemanly exchange in the history of PH.You need to re-read Engineer1's posts again as if he had punctuated them. Two or three times.
The point on which Eng1 and I disagree is the question of which way the bucket flies off when the string breaks: Eng1 is a radial supporter whilst I take the tangential stance.
Tony2or4 said:
The point on which Eng1 and I disagree is the question of which way the bucket flies off when the string breaks: Eng1 is a radial supporter whilst I take the tangential stance.
I don't think he is. Maybe it's me imagining his punctuation marks in the wrong (i.e. right) places! 
grumbledoak said:
Tony2or4 said:
The point on which Eng1 and I disagree is the question of which way the bucket flies off when the string breaks: Eng1 is a radial supporter whilst I take the tangential stance.
I don't think he is. Maybe it's me imagining his punctuation marks in the wrong (i.e. right) places! 
Engineer1: apologies for having suggested that you're a radial man.
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