ashna
A motor boat is rising towards N at 25 Km/hr and the water current in that region is 10 km /hr in the direction of 60° east of south . Find the resultant velocity of the boat .
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ashna
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@waterineyes you know this sum ?
waterineyes
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I don't...
ashna
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you know some one in open study who can help me ?
waterineyes
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I think @sauravshakya can help you here..
ashna
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i sent him a msg .. no reply :/
waterineyes
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But he is online..
Let me try..
ashna
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okay !
waterineyes
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Which chapter is this ??
ashna
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motion in a plane.
waterineyes
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Yeah I think you will get help here..
ashna
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thanks waterineyes :)
waterineyes
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@rsadhvika do you know how to solve this ??
waterineyes
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|dw:1344771481322:dw|
waterineyes
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Here A and B are the vectors..
A is representing the boat and B is representing Water...
ashna
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okay .. understood !
waterineyes
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Now We have to find Resultant first..
For that we first make our figure look like parallelogram..
ashna
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okay
waterineyes
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Wait I draw the figure more clearly for you..
ashna
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its okay .. i can understand :)
waterineyes
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|dw:1344771854805:dw|
ashna
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|dw:1344771963782:dw|
ashna
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is that the parellelogram we need ?
waterineyes
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Now make it look like parallelogram:
|dw:1344771989674:dw|
Getting this ??
ashna
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yeah got it !
waterineyes
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Now can you draw diagonal of the parallelogram ??
ashna
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|dw:1344772085729:dw|
ashna
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wrong ?
waterineyes
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Great..
This is the resultant of A and B vector..
ashna
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okay :)
ashna
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what is theta here ?
waterineyes
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You must mention the direction also..
ashna
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what direction ? direction of vector ?
waterineyes
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|dw:1344772213529:dw|
ashna
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okay !
waterineyes
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Since boat has higher velocity then boat will go in upward direction..
Getting ??
ashna
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yeah ..and if lower velocity , down ?
waterineyes
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Yeah that will depend upon velocity of water..
ashna
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okay !
waterineyes
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Have you studied about the formula:
\[Resultant (R)= \sqrt{A^2 + B^2 + 2AB \cos(\theta)}\]
ashna
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yeah i have !
waterineyes
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Here A is just velocity of boat that is : 25
and B is just velocity of water that is : 10
But you have to find theta first..
Right ??
ashna
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yeah .. how do we find theta ?
waterineyes
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Theta is basically angle between the two vectors A and B..
Here what is the angle between A and B..
Can you locate on the drawing ??
ashna
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|dw:1344772636899:dw|
ashna
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i don't know !
ashna
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|dw:1344772698399:dw|
waterineyes
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That is the angle between A and the resultant..
We have to locate angle between A and B..
waterineyes
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Don't worry @ashna I draw it..
ashna
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okay !
waterineyes
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|dw:1344772809427:dw|
Getting??
That is the angle between A and B..
ashna
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yeah !
waterineyes
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Can you find its value ??
waterineyes
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Make a try..
ashna
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180 - 60 ?
ashna
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120 ?
waterineyes
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Great..
A medal for you..
ashna
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:)
waterineyes
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Can you tell cos(120) = ??
ashna
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yea .. cos (90+30)
- sin 30
- 1/2 correct ?
waterineyes
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I wish I could give you more medals..
Yes that is very correct..
Now can you use that formula ??
ashna
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okay i'll try !
waterineyes
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There is no need to go fast..
I can wait..
Just take your time and post your answer here..
waterineyes
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I think this site is going to be down soon..
waterineyes
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If my reply does not come @ashna then don't worry .
Just post the answer or doubt here I will check it later on..
waterineyes
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What happened @ashna
ashna
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okay .. now i can type .. some net problem i guess.. sorry for the delay .. i got square root 475 !
ashna
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