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![[Post New]](/templates/default/images/icon_minipost_new.gif) 22 Jun 2007 20:05:16 IST
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two trains each of length 100m moving in opposite directions along parallel liines meet each other with speed 50 km/hr & 40km/hr if their accelerations are 30cm/sec sq & 20 cm/ sec sq find the time they take to pass each other
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if you donot face difficulties in life then you are moving on the wrong path--albert einstein |
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22 Jun 2007 20:13:38 IST
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is the ans 3.85 seconds
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22 Jun 2007 20:51:02 IST
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can you tell me the procedure to this
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if you donot face difficulties in life then you are moving on the wrong path--albert einstein |
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22 Jun 2007 21:11:31 IST
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http://www.goiit.com/posts/list/community-shelf-black-holes-18671.htm
visit n rate
thanx
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Hi..........i m a dunce!! just kiddin!! |
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22 Jun 2007 21:43:08 IST
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dude is sarikas answer correct?
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Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.
-Albert Einstein
Generally people who take the piss out of other people hang around in groups of five, because they have a fifth of a personality each.
- Eddie Izzard
It's my life
And it's now or never
I ain't gonna live forever
I just wanna live while I'm alive
-Bon Jovi
By the time a son realizes that his father was probably right, he has a son who thinks he is wrong.
-Anonymous |
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22 Jun 2007 21:50:49 IST
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look u will have to use the concept of relative velocity here
since the trains r moving in opposite dir add the velo
50 + 40 = 90km/hr= 25m/s
add the accn also 30 +20=50cm/s=1/2m/s
now dist = 100m
accn = 1/2 m/s
initial velo = u = 25m/s
use second eqn of mn to get the time
correct me if i m wrong
rate if u like my efforts...
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Put your hand on a stove for a minute and it seems like an hour. Sit with that special girl for an hour and it seems like a minute. That's relativity.
-Albert Einstein
Generally people who take the piss out of other people hang around in groups of five, because they have a fifth of a personality each.
- Eddie Izzard
It's my life
And it's now or never
I ain't gonna live forever
I just wanna live while I'm alive
-Bon Jovi
By the time a son realizes that his father was probably right, he has a son who thinks he is wrong.
-Anonymous |
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hi see see let the name of the trains be A(with 50km/hr) & B(with 40km/hr) now since they are moving in opposite directions therefore velocity of train A w.r.t B = 50+40 = 90km/hr = 25m/sec similarly acceleration of A w.r.t B will become 0.3 + 0.2 = 0.5m/sec^2 therefore it now becomes a case in which train A is moving with speed of 25m/s & acceleration of 0.5m/s^2 has to overtake a stationary train B therefore it's also clear that train A needs to travel 200m to cross train B therefore using s = ut+ 1/2at^2 200 = 25t + 1/2 * 0.5 * t^2 solve for t to get the answer
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"Imagination is more important than knowledge."
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22 Jun 2007 22:15:13 IST
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excellent concept priyesh
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if you donot face difficulties in life then you are moving on the wrong path--albert einstein |
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4 Aug 2007 03:38:46 IST
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yes gud work priyesh
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---------------------------------------------------------------
* Gaurav Ragtah ( aka Artemis Fowl )
* Agent 'G' [sniper] - SD-6 (Alliance of Twelve)
  
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4 Aug 2007 17:34:49 IST
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Given: Two trains move with velocities 50 km/hr and 40km/hr. They move with velocities 30cm/s^2 and 20 cm/s^s. To Find: The time taken to cross. SOLUTION: 30 cm/s^2 = (30/100)m/s^2 = 0.3 m/s^2 20cm/s^2 = (20/100)m/s^2 = 0.2 m/s^2 The acceleration of a body is given by a=dv/dt, dt=dv/a. dt=[(50-40)km/hr] / [(0.3-0.2)m/s^2] = [10km/hr] / [0.1m/s^2] =[10*5/18 m/s] / (0.1m/s^2) =[25/9 m/s] / [1/10 m/s^2] =[(25*10)/(9*1)]. (m*s*s)/(m*s) =(250/9) s = 27.7778 s Hence the time taken by the trains to cross each other is 27.7778 seconds.
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4 Aug 2007 21:24:59 IST
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use relative velocity ur soln size gets reduced.... k see sit on train B say moving wit a speed of 40km/s.... so the train B is nw at rest kk..... nw train A dosnt move wit a speed of 50 bt wit a speed of 50+40= 90km/hr.... nw do the same exercise for their accelerations....k... nw use simple kinematics to gt the answer the asnwer comes out to be...3.856 secs..... IF U LIKE IT THEN PLZZZ RATE ME....!!!
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5 Aug 2007 16:38:23 IST
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very good explanation priyesh.
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A man would do nothing if he waited until he could do it so well that no one would find fault with what he has done ------CARDINAL NEWMAN |
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