Short emails can be interpreted in a variety of ways.
That is one of the problems with email, and why flame wars happen.
But you continue to interpret my comments as ill-intentioned, despite
my explaining that when I smile while asking a rhetorical question, it
is a friendly communication.
I was quite astonished to find that people can get degrees in biology
these days without having passed a basic physics course. When I made
the comment, I was expecting that the people I was talking to would then
pull out their old college physics book and remember what they had been
taught about basic kinematics. Or at least smile back.
To find that many of these quite intelligent people have never had a physics
course in either high school or college, and are making very basic mistakes
in simple physics, is quite surprising. But it makes it all the more important
to me to point out and correct bad physics when I see it in an arena such as this,
where people are going to learn about science. Someone will take it as truth
when it comes from a person who is obviously highly educated in biology, and
never know that this person was ignorant of basic physics.
When a bullet is fired, half the energy does not go into the gun.
Newton's third law is about force, not energy.
When you push against a wall, it pushes back with equal force, or else something
will move. Only when something moves has work been done, or energy transferred.
Underpinning all of biology is physics, and when building things like centrifuges,
it is dangerous to be ignorant of physics. I recommend that everyone on the list
who is still in college should take a basic physics course. And for anyone on the list
who has not taken physics, and is not still in college, a course at a local community
college is cheap, and will make you a better biologist, and a much better DIYbio
equipment builder.
-----
Get a free science project every week! "http://scitoys.com/newsletter.html"On Sat, Mar 10, 2012 at 12:37 PM, Phil <philgoetz@gmail.com> wrote:
On Mar 7, 7:35 pm, Simon Quellen Field <sfi...@scitoys.com> wrote:You apologized, then continued being snarky. A little smiley face
> Did any of you take any physics classes in college?
> :-)
doesn't make insulting people okay.
But Simon is correct. The calculation is not carried out explicitly
in the Wikipedia article, but if you solve for velocity of the rifle
using conservation of momentum, and plug that velocity back into the
kinetic energy equation, you find that about 99.6% of the energy is in
the bullet.
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