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Vectors

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 Joined: 8 Feb 2009 Post: 17
22 Feb 2009 14:08:12 IST
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a girl walks 4km towards west,then she walks 3km in a direction 30 degrees east of north and stops d
Engineering Entrance , JEE Main , JEE Advanced , Mathematics , Vectors

a girl walks 4km towards west,then she walks 3km in a direction 30 degrees east of north and stops determines the girls displacement from her initial point of departure

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Joined: 23 Jan 2007
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22 Feb 2009 14:51:29 IST
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1. 4 km west

2. Effectively 3cos300 km along north and 3sin300 km along east

Net effect : (4-3sin300) km west and 3cos300 km north

Total displacement = {(4-3sin300)2 + (3cos300)2}1/2

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22 Feb 2009 14:53:33 IST
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Let east is x-axis and north is y-axis then displacement of girl is= -4i +3*(0.5i+sqrt(3)*j/2) = -2.5i + 1.5*sqrt(3)jMagnitude of displacement = sqrt(25+27)/2 = sqrt(52)/2

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23 Feb 2009 18:46:05 IST
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{(4-3/2)^2+3cos30}^1/2.

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23 Feb 2009 18:53:04 IST
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sq.root(52/4)

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24 Feb 2009 07:00:02 IST
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New kid on the Block

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24 Feb 2009 07:04:36 IST
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see the above fig.

OP vector=-4i+(3cos60deg)i

=i(-4+3/2)

=-5/2i

vertical component=(3sin60deg)j

=3root3/2

therefore displacement is   =-5/2i+3root3/2j

rate........................................

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