Re: A few silly questions

"Androcles" <Engineer@xxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:4XWyh.292170$MO2.197815@xxxxxxxxxxxxxxxxxxxxxxxxxxxx

I'm engaging in discussion with someone and have found myself going
around
in circles, so I'd appreciate some help with a few mundane questions:

Can velocity change without time?

No.

Can acceleration take place without time?

No.

Is there such a thing as instant acceleration?

Err... instantaneous velocity and instantaneous acceleration
are meaningful terms, the simplest example being the speedometer of a car.
30 mph does not mean you have to travel 30 miles for a whole hour.
30 mph does not mean you have to travel 44 feet for a whole second.
30 mph does not mean you have to travel 0.44 feet for a whole 1/100th
second.

You can make the time interval as small as you like as long as it is not
zero.
Division-by-zero is undefined.

The problem I have with that conclusion is that 'instantaneous' implies a
zero division. Also, as I understand it, 'acceleration' is the measure of
the rate of *change* of velocity and as nothing can change in zero time, I
don't see how accerleration can be said to have taken place.

Is this statement true: "But when no distance is covered against or with
the
force, no work is done
and energy is neither stored nor expended."?

Yes. Work is done when the movement takes place.

Another point that I don't get.

Work and energy are equivalent, they have the same units.
Lift a brick from the floor and place it on the shelf.

Ok.

You
have done work upon it. The brick then has the potential
energy to fall off the shelf, gathering kinetic energy as it falls
and losing potential energy, does work on your toe and
breaks it. Of course that is simplistic, a flywheel can store
energy and not go anywhere.

Of course.

Thanks for your time.

--
AKA "Dobbie The House Elf"

You are welcome, Dobbie. Beware of muggles.
Sorcerer Androcles Dumbledore, Headmaster, hogwarts.physics.

Hahaha... I'll be sure to take heed of your warnings. Thanks for your
input.

--
AKA "Dobbie The House Elf"


.

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