Science Buddies: "Ask an Expert"

I need help choosing a material to do a presentation on. We need to present the physics behind it microscopic, macroscopic and how dense,britlle,youngs modulus ect.
I really need some ideas on any interesting material which will be fun to present and has a lot of physics behind how it works. Thanks

Hi bigbangsam,

Perhaps you could try working with Silly Putty. Not only is it cheap and an interesting material to work with, but it also makes work fun!

One site that has further information is: http://victoria.ac.nz/physics-resource- ... hysics.htm
It looks at both the chemistry and physics behind the material, so take a look and write back if you have any more questions!

Hey thanks for the idea on silly putty but i've decided to go for concrete instead because its so broad and has lots of physics involved. The one thing that im finding hard to understand is the tensile stress and strain of concrete. If you know any websites or if you know yourself that would be great

bigbangsam wrote:the tensile stress and strain of concrete

Well you've confused me as well with your wording.

Ultimate Tensile Strength (UTS), or typically just "Tensile Strength" (TS), is defined as the "stress" that a material can withstand before the material enters a plastic state where "necking" occurs as its cross sectional area significantly diminshes as it is stretched. In this case stress would be force divided by cross sectional area.

Cured concrete tends to fracture instead of entering a plastic state and stretching. For this reason concrete is a very poor material in any application that requires any tensile strength. Prestressed steel reinforced concrete beams are designed so that the steel provides the tensile strength required on the outsides of the beam to prevent fracture, but this requires the steel be under tension (being stretched and pulled straight) when the concrete is poured and while it cures.

Concrete is noted for its compression strength and not its Torsion and Tensil strengths.