Question

What makes a paper clip float?

Asked by: Timothy Hicks

 Answer

A paper clip will not 'float' on water in the same sense that a cork will. If you position a cork below the surface, it will rise to the surface. A paper clip will not.

If you carefully place the paper clip on the surface of calm water, however, you can keep it from sinking because of surface tension. In a liquid, molecules are attracted by neighboring ones in all directions, except for those at the boundary. The unequal attraction of neighboring molecules at the surface forms a kind of 'skin'. This surface tension is responsible for minimizing the surface area of a free-falling drop of water into a sphere.

If you look closely at an object suspended by surface tension, whether it is a paper clip, insect, leaf, etc. you will notice a slight depression in the surface supporting the object. As long as the pressure exerted by an object is low enough, surface tension can support it. Low pressure requires a large area in contact with the water relative to weight.

Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

Search

Loading



Sponsors

USC University of Southern California Dornsife College Physics and Astronomy Department McMaster University Physics and Astronomy Department

Science Quote

'Our loyalties are to the species and the planet. We speak for Earth. Our obligation to survive is owed not just to ourselves but also to that Cosmos, ancient and vast, from which we spring.'

Carl Sagan
(1934-1996)

Deal of the Day

Image of Hover Craft Kit. Click on this image for more info. Hover Craft Kit
Regular Price: $29.99
Today's Price: $12.00
Learn the science behind hover craft technology with this cool kit! Buy it now! Deal ends at midnight!

Top Selling

Here are our physics & astronomy bestsellers:
Mini Plasma Ball
Slide Making Kit
Top Secret - Spinning Top
Wood Grain Newtons Cradle
Deluxe 3D Mirascope
Solar Radiometer
Periscope
Solar Science 4M Kit
Ultimate Chemistry Set CHEM C3000
3D Magnetic Field Tube