Blame that one on me I wrote the question. Now that you point it out you
may be correct. I was thinking that the lowest velocity would generate the
least noise. I really don't know.
Don Mathieson
Tulsa Community College
dmathies@tulsacc.edu
Steve Highland <shighlan@uslink.net>
Sent by: phys-l-bounces@carnot.physics.buffalo.edu
08/25/2008 10:42 AM
Please respond to
Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
To
Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu>
cc
Subject
[Phys-l] One of those Yahoo Answers "URGENT" Physics problems (with a
twist)
I¹ve been horsing around on Yahoo Answers a little bit today and I came
across this question;
------------
Jack is chucking pebbles gently up to Sarah's window, and he wants the
pebbles to hit the window with only a horizontal component of velocity. He
is standing at the edge of a rose garden 8.00 meters below her window and
11.0 m from the base of the wall. How fast are the pebbles going when they
hit her window?
------------
Of course this is an easy problem for a non-beginner. What interests me
is
the assumption that throwing the pebble so it hits the window horizontally
is the ?gentlest¹ throw. I don¹t think so. I would think lobbing the
pebble higher than the window so it came down and struck the pane at a
glancing angle would actually be a gentler impact. But I'm not 100% sure.
It would hit with a lesser horizontal velocity and deliver less of an
impulse to the window, but is that the only thing that matters? I doubt
it.
The duration of contact with the window must play a role, and that time
must
get shorter with higher vertical speeds, right? That would seem to
increase
the force and be bad for the window.
What does govern how ?gently¹ the pebble hits the window? Is my instinct
that a glancing blow at higher speed is gentler than a head-on impact at a
slower speed right or wrong?