Joan Hall

In the car, on the way to drop David off for basketball practice, we got
stuck waiting for a train to pass by. It was a looooong one. Joseph asked
me out of the blue, "How can that one train engine pull all those heavy
cars? I mean, even if there's another engine at the back of the train, that
still so much smaller than all these cars."

I had no idea what to tell him! It had never occurred to me to even
wonder! I had to go and look it up when we got home. Clearly he needs to
be in a real school where a qualified 4th-grade teacher would have known the
answer to his question right off the bat!

</sarcasm>

Joan


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Pam Sorooshian

On 4/17/2009 4:38 PM, Joan Hall wrote:
> I had no idea what to tell him! It had never occurred to me to even
> wonder! I had to go and look it up when we got home. Clearly he needs to
> be in a real school where a qualified 4th-grade teacher would have
> known the
> answer to his question right off the bat!

So - now "I" am off to figure out the answer, too.

I never thought to wonder - and I took a more than 7,000 mile train trip
this year! <G>

-pam

Sandra Dodd

-=-"How can that one train engine pull all those heavy
cars? I mean, even if there's another engine at the back of the train,
that
still so much smaller than all these cars."-=-

The engines are very heavy and strong and the cars are relatively
light. It's not about size, it's about friction. The mass of the
engine puts weight at the front. Steel wheels on wheel rails, once
they're moving, are easy to keep moving. It's easier to keep it
moving once it is moving that to get it started.

Ways to help think about it are to look at roller coasters, and also
to think about an engine going by itself, and then an engine with two
or three cars. Part of the engineering in train engineers is knowing
when to speed up or slow down to make best use of the momentum of the
cars behind the engine, and how not to waste fuel. Like a roller
coaster, the downhills pick up speed. Like a roller coaster, the
most energy/fuel is expended to pull the engine up an incline, but
once the engine is at the top or level, it's not nearly as much work
to get other cars to follow! The engineers will know when a train's
weight needs two or three engines to pull.

Sandra

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Katheryn

Probably has something to do with momentum...once the engine gets going,
the cars glide along the steel tracks. Starting will be the hardest, as pulling
up any kind of incline.
Katheryn
----- Original Message -----
From: Joan Hall
To: [email protected]
Sent: Friday, April 17, 2009 6:38 PM
Subject: [UnschoolingDiscussion] Why ordinary folks like me aren't qualified to educate their own children :-)





In the car, on the way to drop David off for basketball practice, we got
stuck waiting for a train to pass by. It was a looooong one. Joseph asked
me out of the blue, "How can that one train engine pull all those heavy
cars? I mean, even if there's another engine at the back of the train, that
still so much smaller than all these cars."

I had no idea what to tell him! It had never occurred to me to even
wonder! I had to go and look it up when we got home. Clearly he needs to
be in a real school where a qualified 4th-grade teacher would have known the
answer to his question right off the bat!

</sarcasm>

Joan

[Non-text portions of this message have been removed]





[Non-text portions of this message have been removed]