Re: The opposing rockets and the box

Michael Moroney wrote:
"Spaceman" <spaceman@xxxxxxxxxxxxxxxxxxxxxxxxxx> writes:

Michael Moroney wrote:
Wow is right. Space***, it's rather strange to see you rail on why
relativity is wrong when you don't even seem to know high school
physics. Think about it. When that cannonball gets fired into that
lump of clay stationary in space, does the cannonball/clay lump
move:

1) not at all
2) slower than the cannonball before impact
3) the same speed as the cannonball
4) faster than the cannonball

Of course it would be 2 Mike.

So tell us more (if you can). If you know the mass of the
cannonball, and its velocity, and you know the mass of the clay lump
and know its velocity is initially 0, what is the velocity of the
combined mass after impact?

It would of course be greater than 0 along with
it's new kinetic energy being greater than 0.
so.. with a greater than 0 KE there is no
way you will get the original KE that started the motion
to stop the greater KE now occuring to the larger mass.



But the problem is Greg is ignoring the actual
difference when he gets back to m*v all over again.
The small ball was m*v alone and now he has the
larger and small ball being m*v again.
He might as well have not done any math to
come up with m*v all over again.

Can't you follow his math? This is high school level.

His math is ignoring the greater KE that larger mass
would have.


How fast is the stuck-together car/truck moving? Why is it moving at
that speed?

Again,
It is moving faster than it was originally (0 speed)
and because such it now also has a non zero KE and
it will take more KE to stop it than it took to move it.
Sheesh Mike,
this is all classical pre-highschool stuff.
:)


OK, you tell us. After the first impact, a second 1 ton subcompact
travelling the opposite direction at 10 mph crashes into the stuck-
together car-truck, and sticks. How fast is the resulting
car-truck-car mass moving, and why is it moving at that speed?

It won't be stopped.
You don't have enough KE coming from the new impact to
do such.

--
James M Driscoll Jr
Spaceman


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