Try this. Energy is the capacity to do work. Work is force*distance. Let the work not accelerate anything but overcome friction at low speed. Let a 10 kg block sit on a table and have a coefficient of friction of 0.1, so the constant force to move it slowly (without acceleration) is 1 kg. If the energy in question is 4 kg-meters (converted suitably to common units), the block can be pushed 4 meters. This avoids time, velocity, and specific heat, keeping the whole thing purely mechanical for intuitive appeal. Steve Gray ----- Original Message ----- From: "Jason Holt" <jason@lunkwill.org> To: "math-fun" <math-fun@mailman.xmission.com> Sent: Monday, July 17, 2006 1:52 PM Subject: Re: [math-fun] Another physics question
On Mon, 17 Jul 2006, Eugene Salamin wrote:
and is there an intuitive way to explain the conversion from the 30mph baseball's energy into kg*m^2/s^2 without calculus?
Perhaps, think of measuring the energy calorimetrically, by converting the energy into heat. Let a tank of water bring the baseball to a stop, and measure the temperature rise. This doesn't explain what energy actually IS; I can't think of a simple answer to that question.
The 30mph baseball is my favorite intuitive notion of energy. Batteries are another one I like to use when explaining it; compressed springs are good, too. I've used calorimetry examples as well, although those can be difficult since specific heat isn't as intuitive for people.
What I was really trying to get at is that since momentum is, at least to me, a more intuitive way of understanding energy, why do we teach energy in terms of kilograms accelerated for a distance? And secondarily, what's the formula for converting a moving baseball into an accelerating kilogram, and how can I explain it to people who don't know calculus?
-J
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