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Verbatim question for GR8677 #1
Mechanics}Newtonian

This problem can be translated into an equation:


Note that the sign is compensated for. \dot{x} is positive going up (so that -k\dot{x} acts in the same direction as gravity), and it is negative going down (acting in the opposite direction of gravity).
\par

(A) \ddot{x}\neq g \forall t because \ddot{x}=\frac{1}{m}\left(-k\dot{x}-mg\right)

(B) True. \dot{x}=0 at the top. Thus, plug that into the equation in described in (A) and get \ddot{x}=-g

(C) \ddot{x}=\frac{1}{m}\left(-k\dot{x}-mg\right) could be greater than g, especially when \dot{x} is positive in sign.

(D) The wind friction (-k\dot{x}) term would change sign when going downwards. (See the Note above.) Thus, the equation of motion presented above would be different in sign going down and up. (Also, one could argue that after the force of wind friction acts, to conserve energy, kinetic energy must lessen in the final energy sum. Thus, the final velocity can't be the same as v_0. Or, intuitively, one could see friction as a symmetry breaker, viz., the ideal parabolic path is disturbed in such a way that the end velocity changed.)

(E) Since the force other than gravity is a frictional force, which, by definition, slows down the object, the final velocity has to be less than v_0.

See below for user comments and alternate solutions! See below for user comments and alternate solutions!
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Comments
nomdaq
2014-07-20 16:23:49
the solution is not clear to me. kindly tell me the net force acting own the stone. why we have taken -mg here.
JinjunDing
2014-10-19 17:30:44
you are not right
Answered Question!
drs2872
2013-08-08 22:20:58
How should I start preparing for GRE Physics test, I just have two months in hand? Which study material should I refer to get the exact depth of syllabus?
iskhar ali
2013-09-01 02:54:26
I have also apply for the GRE physics see and study the outline of gre and old papers of gre physics and memorize physics formulas .

NEC
saifi_786
2011-08-22 21:00:49
can I download the answers of these books?
NEC
chandanjumech
2011-05-17 06:14:38
I am preparing for gre physics. Is it necessary to be appeared in gre general.
lee
2011-08-16 08:26:16
Yes, Universities ask for both physics GRE as well as general GRE scores.
NEC
atp_ch
2010-08-17 05:43:03
testNEC
yosun
2010-06-27 17:47:06
testing123 \langle my \rangle NEC
yosun
2010-06-27 17:46:29
testing 123NEC
withuman
2008-04-30 23:08:04
\frac{a}{b}NEC
shashiprakash
2007-07-23 23:38:47
shouldnt be the sign of mg be taken as positive in the equation which has been formed in the solution......if we see in terms of force,than ( m*g-k*v) shows us that effective force is reduced hence the there will be less acceleration than g...what are the standard sign conventions for taking g forceNEC
abcdefg
2007-06-01 22:53:59
testNEC
BABU G
2007-03-15 21:47:37
how to get a copy of GR8677 and others
hamood
2007-03-24 17:13:27
If you go to this link http://www.physics.ohio-state.edu/undergrad/ugs_gre.php

and scroll down to the very end, you will find the 4 released gre exams.
hamood
2007-03-24 17:15:49
http://www.physics.ohio-state.edu/undergrad/ugs_gre.php
NEC
brandnewus
2007-02-25 03:00:59
this is a test message with \LaTeX and 'quotation's' ... and a complicated equation like \frac{\sum^\infty_n x_n^2}{\sqrt{x+\gamma}}Typo Alert!
eltha
2006-12-17 09:19:34
is there any way i can get a copy of the test: GR8677, GR0177, GR9677, GR9277?

seba240698
2006-12-18 01:56:11
Yes, could you tell s how to get hold of the tests GR8677, GR0177, GR9677 and GR9277?
yosun
2007-02-21 14:16:04
Yes, I'll post the original problems here next to the problems in the next few days or weeks. I know how hard it is to get a copy of the problems if you don't know the right people (and can't afford the thousand-dollar eBay bids...) Hopefully, that'd help.
yosun
2007-02-21 17:37:25
yeah, and will also redesign this site, perhaps..
yosun
2007-02-25 01:47:35
ok, the GR9277 original questions have been posted!
kainnat
2009-02-17 10:12:53
is there any way I can get a copy of the test:
GR86-2
GR90-16
GR91-17
GR91-18
GR91-19
GR92-1
GR92-2

kainnat
2009-02-17 10:14:35
I am preparing for general and physics gre . I got a lot of information for physics but not for general. so anybody will help me . Thanks.
NEC
eltha
2006-12-17 09:13:57
NEC
x111
2006-10-29 00:03:38
try http://www.hcs.harvard.edu/~twiki/bin/view.cgi/SPS/PhysicsGREResources?rev=1.5 />
GRE papers and a lot of physics study materials are also there.
NEC
caseycsh
2006-06-06 19:59:25
I tried to browse thru the website of Brandeis but couldn't log into it. How should I get a copy of the test, Yosun?NEC
asm3j
2005-11-10 06:32:30
is there any way i can get a copy of this test?

yosun
2006-01-13 14:27:15
Brandeis has all 4 released GRE Physics exam years available online:

http://www.physics.brandeis.edu/undergraduate/GRE_physics/GRE.html

FYI: This includes GR8677, GR0177, GR9677, GR9277
NEC
asm3j
2005-11-10 06:32:05
NEC
jet
2005-11-08 11:18:04
NEC

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