A train starts from a station P witha uniform acceleration A1, for some distance and then goes with uniform retardation A2 for some more distance to come at rest at the station Q. The distance between stations P & Q is 4km and the train takes 4 min. to complete the journey , then 1/A1+1/1A2  =

Asked by SIDDHARTH SHARMA | 24th Nov, 2014, 11:03: AM

Expert Answer:

There are two case in given question:
1. when train moves with uniform acceleration
2. When train moves with uniform retardation.
 for first case,
Let a train starts from a station P with uniform accleration A1, let u1 be the initial velocity and t1 be the time when it reaches at some distance s1
From kinematic eqution of motion we have,
v1=u1+A1t1         (u1=0 Initialy at rest)
v1=A1t1 .........(i)
 
begin mathsize 14px style straight A subscript 1 equals straight v subscript 1 over straight t subscript 1 end style.........(ii)
For second case the final velocity of first interval will be intial velocity of second. Let A2 be uniform retardation t2 be the time when it travles a distance s2 and comes to rest .
From kinematic equation of motion we have,
v2=u2-A2t2=v1-A2t2    (v2=0 finaly comes at rest)
v1=A2t2         (iii) 
 
begin mathsize 14px style straight A subscript 2 equals straight v subscript 1 over straight t subscript 2 end style         (iv)
Using kinematic equation of motion,
 
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Answered by Priyanka Kumbhar | 25th Nov, 2014, 11:00: AM

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