[SI-LIST] Re: HSDD: Re: SI Position Open READ THIS!!!!
- From: "Todd Westerhoff" <twester@xxxxxxxxxxx>
- To: <Richard.Kim@xxxxxxxxxxxxxx>, <arpad.muranyi@xxxxxxxxx>,"'Si-List@Freelists. Org'" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 31 Jan 2002 09:38:54 -0500
As I remember it:
f = ma
You're saying when f = 0, somehow a > 0?
Is this some kind of new math?
Todd ;-)
Todd Westerhoff
SI Engineer - Hammerhead Networks
5 Federal Street - Billerica, MA - 01821
email:twester@xxxxxxxxxxx - ph: 978-671-5084
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Kim, Richard
Sent: Wednesday, January 30, 2002 9:05 PM
To: 'arpad.muranyi@xxxxxxxxx'; 'Si-List@Freelists. Org'
Subject: [SI-LIST] Re: HSDD: Re: SI Position Open READ THIS!!!!
I am not sure if you are applying Newton's law correctly.
When you press the clutch, you are removing the rotational
force on the wheels.
Think of hitting a golf ball. After the impact, the applied
force is no longer there. Applied force being mass and
acceleration of the club head.
Does the ball reach the highest speed at the impact and
slows down immediately?
Although the applied force has gone away, the ball should continue
accelerating until it meets opposing forces.
Now the force on the ball is the mass x acceleration of the ball.
If there was no air resistance and gravity, according to Newton's law
the ball should have constant acceleration resulting in increase in speed.
At the point of impact, the ball receives a force = mass of club head
x accel of club head. Due to air resistance and gravitational pull the
the ball immediately starts to decrease its acceleration, but still
increasing
in speed until acceleration becomes zero.
So getting back to car example, if there were no air resistance, friction
from the wheels and no gravity, the acceleration of the car would be
constant
therefore increasing in speed.
If the acceleration was high enough, it wouldn't be surprising to see
some increase in speed while acceleration goes down to zero.
Richard
-----Original Message-----
From: Muranyi, Arpad [mailto:arpad.muranyi@xxxxxxxxx]
Sent: Wednesday, January 30, 2002 11:16 AM
To: 'Si-List@Freelists. Org'
Subject: [SI-LIST] Re: HSDD: Re: SI Position Open READ THIS!!!!
Rob,
Shouldn't have mailed your response to the list just yet...
I started to get some private replies with the guesses for
the answer. I was beginning to feel tempted to take score
and post it to the reflector after a bunch of replies came
in...
Anyway, you are correct. I might just add, that the speedometer
may not even have to be mechanical to exhibit this effect. Think
about how an electronic one may work. It would have to sample at
least two samples of whatever part's (drive shaft, etc.) position
it measures with respect to time. Then it has to do some calculation
to display the number as the speed of the car, which also takes time...
Of course they could also put a magnet on the moving part and a coil
next to it and measure the voltage it generates as an analog signal
that is proportional to the speed of the car resulting in a real time
readout. But even then we would still have the mass of the needle to
deal with...
Regarding the rest of your writing, and the laziness of students, I
agree, there is a problem there too. We ALL have our share of
strengths and shortcomings, and I didn't mean to point my fingers
at the professors alone, because I have met very good ones too in
my life. I feel I had to mention this before it got too late and
the mud began to fly around...
Arpad
===================================================================
-----Original Message-----
From: Rob Szalapski [mailto:Rob_Szalapski@xxxxxxxxxxxxxx]
Sent: Wednesday, January 30, 2002 12:17 PM
To: arpad.muranyi@xxxxxxxxx; 'Si-List@Freelists. Org'
Subject: RE: [SI-LIST] Re: HSDD: Re: SI Position Open READ THIS!!!!
You have me curious about the clutch. Here is what I think. Most
mechanical automobile gauges have some type of mechanism that involves a
spring and something that opposes the spring, like an electric magnet
operated by a spinning cable. If you were to accelerate really fast, like
you are describing, you should expect the needle to overshoot the correct
mark by a significant amount, then oscillate about the equilibrium point,
the gauge being almost unreadable. To correct this you overdamp the system
so it relaxes exponentially to equilibrium. Your car is fine; Newton is
fine; your gauge has a delay.
I would hate to think of that during an interview.
By the way, I am a high-energy particle physicist/theorist, though I did
spend a lot of time in a chemistry lab when an undergrad. I do software
these days -- pays better than quantum field theory.
I have tutored, TA'd and taught many courses. The problem is not so much
the curriculum, but the quality of the students. Good students are curious
and go looking beyond what is required. Most are lazy and do nothing more
than what is absolutely required.
Students should learn theory in the class. Then they should work with a
research group in the lab on the side and try to do internships in the
summers. That is the only way to cover all of the bases. I worked as an
undergraduate RA in graduate research labs while I was a student, and that
is just part of the experience. Any decent engineering department should be
working hard to get students into internships and/or labs.
Unfortunately it is very hard to get good students these days unless you are
in the school of business. There you can be lazy and only marginally
intelligent and still make much better money than a hard working, very
intelligent engineer. (It's even worse for research physicists!)
-- Rob
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