Untitled Document

Physics Demo Number: 185

Approximate

Run Time: 3 min

Vertical Bucket Swing in a Circle

Demo Description

Swing a bucket, with water in its bottom, around in a vertical circle .

One sees that its circular motion can prevent spillage of any water.

Repeat with the water replaced by styrofoam peanuts, but with slower angular speed of rotation to see a spillage mess.

Scientific Principles

If the net central force needed to rotate a bucket in a vertical circle exceeds the gravitational force on the bucket,then water in the bucket will not fall out when the bucket is moving through inverted orientation regions of its circular motion.

Equipment

Bucket
Styrofoam Peanuts

Equipment Location

Kit (185) on [B-3-3]
Kit (053) on [C-1-5] contains another bucket.

Instructions

The apparatus is seen in the picture. One should only use slow speeds to show spills, with the Styrofoam contents - not with water as the contents.

Spilled water is risky around the computers and the interface in the lecture halls.

One should also make the vertical plane of the bucket motion parallel to the front board, to avoid launching the bucket into the seated class in the event of grip failure or handle failure.

If one insists on flashy showmanship, having one bucket with the peanuts concealed under the lecture table will allow switching the water bucket for the peanut bucket and then slowing down to let peanuts spill out, instead of the expected water.

The peanuts are light enough to preclude handle failure during the swing.

This will allow one to turn the vertical plane of the bucket motion so that the contents can head toward the students PROVIDED you practice the safety of your grip ahead of time.