Science problem!?

Question

Place three wooden dowels with different diameters on lumps of clay. Put a heavy book on top of each dowel. Which dowel sinks deepest into the clay, the one with largest diameter or the one with smallest diameter? Please explain it.
Thanks!

Answer 1

The one with the tallest lump of clay sinks deepest, eventually.

If the lumps are identical sizes and time is not limited, they will all sink the same, just different rates.

If you are limiting the time they have to sink into identical lumps of clay with identical books balanced atop the dowels, the skinniest dowel sinks the most in the shortest time. It is a surface area thing.

The biggest-diameter dowel has the biggest surface area. The weight of the book is more spread out. So assuming that the clay is a semi-firm clay, it will have a certain "bouyancy" - the ability to support weight via displacement. Think of how a pile-driver works - and why. Same concept. More piles = bigger EFFECTIVE surface area = supports more weight for the same type of load.

Here's a different little thought experiment for you. Get a girlfriend to walk on your back with high heels in chunky, "walking", and stiletto styles, then see which time you get the worst welts. See which one hurts the worst. That will convert the problem into something where you can REALLY do a thought experiment.

Yeah, I know... kinky. But sometimes you need to spice up your lessons to make them stick.

Answer 2

the one with the smallest diameter.

ok the reason the one with the smallest diameter will sink further is because there is less area of the dowel touching the clay. Presure is equal to Force per area so the same force over a smaller area gives a greater amount of presure.

Answer 3

Smallest diameter, because the area of contact with the clay is less. Intuitively, which knife cuts better usually, a razor shapr instrument or a dull plastic sword. There is greater force per area of surface contact. I wanted to use the buoyancy argument (Archimedes Principal) but this is not a liquid you are floating thing on.