**23**
Abhishek Priyam
**·**2009-03-23 04:17:50
Ship B sees that it is heading to A or ship A sees so or observer from ground see that...

I think ship B sees that...

**1**
satan92
**·**2009-03-27 23:06:01
the second one is even easier!

let the angle at any instant be θ to the horizontal

then we have

dr/dt=vcosθ-u

and

dθ/dt=-vsinθ/r

so dt=dr/vcosθ-u

(u-vcosθ)dθ/vsinθ=dr/r

integrating we get .

log(cosecθ-cotθ)^{u/v} - logsinθ=log(r/d)

we get

r/d=(cosecθ-cotθ)^{u/v}/(sinθ)

thus

r/d=(1-cosθ)^{u/v}/(sinθ)^{(u/v)+1}

**66**
kaymant
**·**2009-03-27 23:12:29
This was my solution to the first part: the concept of invariance.

**26**
eureka123
**·**2009-03-27 23:29:54
sorry sir par kuch samajh nahin aaya.....[2][2]

**66**
kaymant
**·**2009-03-24 23:35:13
yes the situation is like what you have shown..

**96**
Asish Mahapatra
**·**2009-03-23 23:50:39
ans is correct for 1st question .. provide solutions ...

**26**
eureka123
**·**2009-03-24 23:53:43
ok sir........will try to do further.......[1][1]

vaise what are its chances of coming in JEE??

becoz it looks a bit lengthy.......

it tried to form a 3-4 eqn but nothing gained out of them[2][2]

**26**
eureka123
**·**2009-03-23 23:58:35
At time t is the situation like this??????

If yes then i will try to do it

**26**
eureka123
**·**2009-03-24 00:02:51
anyways 2 things are clear........

dx/dt = u cosθ

and dy/dt = usinθ

what next????[12][12]

**66**
kaymant
**·**2009-03-27 23:59:16
eureka123, kaun sa argument samajh nahi aaya?

**1**
Jijo Sagai
**·**2018-05-25 07:04:24
How come vcosA - v = v(1 - cosA)??? In Vca?

**1**
satan92
**·**2009-03-27 21:45:11
the first one is not lengthy at all ..

we have if the line joining the two particles makes an angle θ with the horizontal ..

and if the distance between them is r

dr/dt=(ucosθ-u)

intial r=d final let D

w get

D-d=_{0}∫^{t}ucosθdt -_{0}∫^{t}udt

further we have

final distance D also= ∫udt-∫ucosθdt

so we get D-d=-D

D=d/2 =1/5

**1**
satan92
**·**2009-03-27 21:46:02
d/2=1.5 not 1/5 as mentioned sry

**26**
eureka123
**·**2009-03-30 12:49:38
sir pehle to iska matlab bataoo.....**."""the concept of invariance.""'**