Whirling a bucket full of water

[Himal kharel]

when a bucket with water is whirled in vertical circles in sufficient speeds the water remains there.
Can you explain me in terms of centripetal force not centrifugal or inertia.

 

[Naty1]

Centripetal force acts inward toward the center of rotation...it keeps the bucket in place.

Centrifugal force is the opposing force that holds the water in place.

 

[timthereaper]

The centrifugal force is the force you would feel if you were in the rest frame of the water. There would be this force pushing you into the bucket as the rest of the world was rotating.

The centripetal force of the bucket is keeping the bucket in the circle of rotation. The water wants to keep moving tangent to the circle of rotation but the bucket pushes the water back toward the center, thereby changing its direction.

 

[rcgldr]

Can you explain me in terms of centripetal force not centrifugal or inertia.

No because forces only exist in equal and opposing pairs, Newton's third law. In this case, the Newton third law pair of forces are the centripetal force, and the outwards reaction force (centrifugal reaction force) due to centripetal acceleration. The other third law pair of forces is due to gravity, an atractive force that pulls the water towards the earth, and pulls the Earth towards the water (the same goes for the person, the bucket, and anything else affected by gravity).

 

[harrylin]

No because forces only exist in equal and opposing pairs, Newton's third law. In this case, the Newton third law pair of forces are the centripetal force, and the outwards reaction force (centrifugal reaction force) due to centripetal acceleration. The other third law pair of forces is due to gravity, an atractive force that pulls the water towards the earth, and pulls the Earth towards the water (the same goes for the person, the bucket, and anything else affected by gravity).

Yes indeed; the clue for the water staying in place is the centripetal acceleration, which must be, I think, at least equal to the gravitational acceleration. But it's not a very simple problem due to the angle that the bucket opening makes relative to gravity; I suppose that the water starts falling sidewards and that therefore also the rotation speed matters. :tongue2: Perhaps someone else can elaborate?

 

[kcdodd]

Centrifugal force only appears in a non-inertial reference frame. Assuming you're describing this in an inertial frame there is no centrifugal force. The force pair is the centripetal force of the bucket acting inward on the water, which causes the water to follow a circular path, and the force of the water back on the bucket. This is not the centrifugal force, because it is acting on the bucket not the water.

On the up-stroke, if the bucket suddenly disappeared, the water would fly up away from the ground, because it is going up at that point. If the bucket is spun fast enough it causes the water to come back down faster than gravity would have caused it to (total force = centripetal > gravitational), and so the water sticks to the bottom of the bucket because it must push on the water to do this.

 

[Himal kharel]

when a bucket full of water is whirled in sufficient high speeds, it requires a high centripetal force which cannot be provided by the weight itself as Mg<Mv^2/r , so the water has to push against the bottom of the bucket in order to provide necessary centripetal force in form of reaction. so water stays there.

but at less speeds i.e. small centripetal force a small part of weight can provide the centripetal force as Mg>mv^2/r and rest of the weight accelerates it.

 

[Drakkith]

when a bucket with water is whirled in vertical circles in sufficient speeds the water remains there.
Can you explain me in terms of centripetal force not centrifugal or inertia.

The centripetal force holds the bucket and water against the centrifugal force caused by the bucket and water. One cannot separate the terms and still come up with a sufficient answer.

when a bucket full of water is whirled in sufficient high speeds, it requires a high centripetal force which cannot be provided by the weight itself as Mg<Mv^2/r , so the water has to push against the bottom of the bucket in order to provide necessary centripetal force in form of reaction. so water stays there.

but at less speeds i.e. small centripetal force a small part of weight can provide the centripetal force as Mg>mv^2/r and rest of the weight accelerates it.

The centripetal force is directly determined based on the mass and rotational speed of the object. At low speeds the centrifugal force falls to such a low amount that it cannot overcome gravity and the bucket and water enter free fall towards the top of the rotation. At even lower speeds the bucket and water can't even complete one rotation and end up falling.

 

[Pythagorean]

The waters trying to go straight from it's momentum given to it a momentago, but you keep pushing it towards the center of rotation with the bucket.

 

[timthereaper]

when a bucket with water is whirled in vertical circles in sufficient speeds the water remains there.
Can you explain me in terms of centripetal force not centrifugal or inertia.

Why are you limiting the possible explanations? I've noticed you've had a few posts with similar restrictions. Do you not understand these concepts (i.e. centrifugal force or inertia)? I'm sure there's about ten people here that would take the time to explain them to you.

 

[harrylin]

Note that with gravitation but without inertia, there would only be gravitational force. Then it is impossible for the water to stay in the bucket.