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Re: Centrifuge in "World Book"



Howdy-

From: Chuck Britton Sent: 5/20/01 9:01 PM

The colloquial use of heavier to mean denser is probably the blunder
under question.

For most people, this isn't a slip of the tongue. That is, denser objects
often feel heavier than less dense objects.

Just the other day, a colleague asked me to help her carry a couple of boxes
to the car. I picked up the bigger box, but she said, "Take the small one,
it's heavier than the large one," so I swapped. The big one didn't seem
lighter to me, and I convinced her to let me mass them. The big box was in
fact 6 kg while the small one only 4 kg.

She was really surprised. Obviously she didn't mean density. She honestly
believed that the larger box was harder to lift (neither was particularly
bulky) than the smaller one.

She is hardly alone. I spend a fair bit of time with my students at the
start of each year playing with the mental illusion that is at work here.
They lift boxes filled with styrofoam that they will say are lighter than a
1 kg cylinder when in fact they are two or three times as massive. Even
asking about density doesn't change their mind.

I learned in a couple of history of science classes that it was hard for
people to buy into the idea of mass as being independent of size (Archimedes
notwithstanding). Quantitative chemistry was a long time coming.

Marc Kossover