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From: "Robert Cohen" <Robert.Cohen@po-box.esu.edu>
Subject: Re: [Phys-l] A simple (?) question about speed
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
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<47F49E5A3B3AA84F8DD701A3C515BF7B026920BD@tigger.admin.esu.edu>
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I also asked my colleague to ask the same question on her exam (as
"bonus") with the info about unknown changing speed included. Here are
her results:
At a certain moment, a car is moving toward the left at a speed of 30
m/s along a horizontal surface. You are given no information on whether
it is slowing down, speeding up or moving with a constant speed. What
is its acceleration?
A. 30 m/s2 (5)
B. 30 m/s (6)
C. Zero (5)
D. Cannot be specified without more information. (12)
My colleague also asked her students to provide a written rationale for
their answers. When I have some more time, I will go through and see if
I can find a pattern.
----------------------------------------------------------
Robert A. Cohen, Department of Physics, East Stroudsburg University
570.422.3428 rcohen@po-box.esu.edu http://www.esu.edu/~bbq