This is interesting - mainly because many of my students definitely see it
the other way. Consider the act of catching a ball. Many students would say
that the ball is exerting a force on your hand BECAUSE of the fact that you
are decelerating it. They ascribe a force to inertia. If you attempt to
accelerate or decelerate an object its inertial properties will produce a
force countering your attempts at changing its speed. Newton's 3rd then has
your hand produce an equal and opposite force ON the object. So acceleration
becomes the cause and force the effect.
Bob at PC
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of JMGreen
Sent: Thursday, April 27, 2006 2:21 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Equations
This list has a way of waving its hands a lot -- as if we were
dealing with a oral exam. The original question was what is in your
head when you see the equation F=ma. Joe Belina(sp) gave a
straightforward reply. Thank you
Q1) In F=ma do you (not your students -- not for a doctoral oral) --
do you now think of F as force or as acceleration?
If i push on a block with my hand and the block accelerates, don't
I think of the push as a cause and the acceleration as the
result? Then I think of F=ma and say to myself aha I know a law
which applies. In this case the push is F and the acceleration is
a. Here F is a cause and a is the result.