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![[Post New]](/templates/default/images/icon_minipost_new.gif) 5 Jan 2008 22:57:59 IST
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1.The velocity of a particle varies with time as v=t2-t,where t is time in second.the time for which the particle will perform retarded motion is
(A) t<1/2
(B) t>1/2
(C) 1/2 <t<1
(D) 0<t<1
2.A ship B is steaming on a straight course south-east at a uniform speed of 15km/hr.Another ship A is at a distance of 10km due north of B and steams at a speed of 12km/hr.The minimum distance between the ships will be:
(A)10 km
(B)9 km
(C)9.9 km
(D)8.8 km
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Destiny is no matter of chance.It is a matter of choice.It is not a thing to be waited for, it is a thing to be achieved. |
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5 Jan 2008 23:01:23 IST
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hey, these questions were in brilliant's Y.G.FILE
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1st year,
B.Tech ( CSE ) ,
NIT-Trichy.
"There are no accidents in my philosophy. Every effect must have its cause. The past is the cause of the present, and the present will be the cause of the future. All these are links in the endless chain stretching from the finite to the infinite." - Abraham Lincoln |
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5 Jan 2008 23:06:27 IST
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(1)
v = t2-t
dv/dt < 0
2t-1<0
t< 1/2
(2)
Direction of steaming of B is not clearly defined..So I'm solving it taking the dir as south-east just like A ..
The velocity of approach of the ships = 12cos45o - 15cos45o= -3/ 2
As the velocity of approach is negative, the initial distance would be the minimum distance.!!
Thus, both answers are option A
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5 Jan 2008 23:08:46 IST
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@ goiit_user
both ur answers are wrong....
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5 Jan 2008 23:19:36 IST
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a = dv/dt
a = 2t-1 < 0 (for retarded motion)
so, t < 1/2
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Bipin Kumar Dubey
Chemical Dept.
IIT Kharagpur
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5 Jan 2008 23:21:22 IST
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Thats whatt I did..
t<1/2
@mastermind
If its wrong, then whats the right answer??
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5 Jan 2008 23:23:40 IST
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Yes,I dont see whats wrong with t<1/2...
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5 Jan 2008 23:24:14 IST
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ansr 4 1st one....well the cncpt applied by goiit_user were crct...here's d soln
dv/dt<0
dv/dt=2t-1
hence ur ansr is (A)
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5 Jan 2008 23:30:35 IST
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2t-1 < 0
gives t <1/2 which is A
and not t>1/2 which is B
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5 Jan 2008 23:34:44 IST
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i have a doubt-in which direction does B steam?
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5 Jan 2008 23:36:29 IST
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My solution takes the direction of B the same as that of A!!
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5 Jan 2008 23:40:53 IST
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Then i really dont see why it is wrong...the previous one too!!
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5 Jan 2008 23:44:20 IST
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The forum creator isn't even giving the right answer!!!
Lets skip the thread now!!
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5 Jan 2008 23:48:04 IST
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i agree with option A for 1st question but no guess abt 2nd because of direction confusion, plz chk qustn
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6 Jan 2008 20:08:01 IST
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even I got (A).but the answer given is (C)...
here's the soln as given...
v=t2-t
acc.=dv/dt=2t-1
velocity reverses its direction at t=1 sec and acceleration reverses its direction at t=1/2 secs.
hence ,when 1/2 <t<1,v is negative and a is positive....
I think that the answer is wrong...plz express ur views
What abt the second question ...anybody plz solve it....
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