Re: [Phys-L] escape speed

[Matthew Heaney <matthewjheaney@gmail.com>]

On Thu, Aug 1, 2024, 18:20 Anthony Lapinski via Phys-l <
phys-l@mail.phys-l.org> wrote:

> I teach about gravity early on in my high school astronomy course. I
> discuss/derive surface gravity, orbital speed, and escape speed. And then
> we do comparative fractions. I want to add some ideas about
> their importance. I know that gravity affects atmospheres of planets and
> stars, and is used to calculate physical properties of stars. What about
> escape speed? Is it mostly important for space travel? But isn't gravity
> the main factor here?

The issue is how much work you do against gravity - it's about energy, in
other words.  The existence of gravity is why you're sitting in a potential
well (you're bound, so it's negative), and you need enough kinetic energy
to get back to zero.

Force and energy should always be discussed together.  Force is simply the
mechanism by which your change your energy.

But to derive the escape velocity, you need to be thinking about energy.
The only thing that matters is your speed (that is, your kinetic energy).

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