Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Kinematics First

In a message dated Tue, 17 Sep 2002 8:42:20 AM Eastern
Standard Time, I wrote:

I agree with this 100%. That is why I leave it
[kinematics] until after dynamics. I
believe dynamics allows students to explore acceleration on
a conceptual
level.

On Tuesday, September 17, 2002 11:35 AM, Justin Parke asked:

Could you give an example of how you might introduce dynamics
and acceleration simultaneously?

Before I do dynamics, I make sure the students understand speed, ratios and
various other problem-solving techniques.

The class explores the problem of an object that is falling (I use a video
clip of Rabbit falling down Gopher's hole; from Winnie-the-Pooh), which I
use to introduce the idea of applying generalized laws and theories.

First, I have the class explore what we mean by force. We use force meters
to investigate what is meant by Newton's 3rd law. This gives them the
opportunity to distinguish between "force" and "effect" and the various
types of forces (as well as what it means for a force like gravity to be a
non-contact force).

Then, they investigate the effect of forces on objects. They explore the
meaning of "net force" and what is meant by Newton's first law. They
investigate what "direction" means in terms of forces, velocity and
displacement. This is when I introduce the idea of "vectors".

We then apply this to falling objects. We first make the assumption of no
forces except gravity and see if it reproduces the observed motion. We find
that the force of gravity is proportional to mass. We find that a constant
force produces a constantly changing velocity, at which point I introduce
the term "acceleration".

They then investigate what is meant by Newton's 2nd law and use it to
predict the acceleration of an object, which they then use to predict the
velocity and the displacement (kinematics). They then compare this to
reality and investigate the validity of the assumptions used.

Does this help? Am I misusing the term "dynamics"?
____________________________________________
Robert Cohen; rcohen@po-box.esu.edu; 570-422-3428; http://www.esu.edu/~bbq
Physics, East Stroudsburg Univ., E. Stroudsburg, PA 18301