Dot product of a vector with vectors  are respectively – 1,

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 Multiple Choice QuestionsLong Answer Type

201.

Let straight a with rightwards arrow on top space equals straight i with hat on top plus 4 straight j with hat on top plus 2 straight k with hat on top comma space space straight b with rightwards arrow on top space equals space 3 straight i with hat on top space minus space 2 straight j with hat on top space plus space 7 straight k with hat on top space and space straight c with rightwards arrow on top space equals space 2 straight i with hat on top minus straight j with hat on top minus 4 straight k with hat on top. Find a vector straight d with rightwards arrow on top which is perpendicular to both straight a with rightwards arrow on top space and space straight b with rightwards arrow on top space and space straight c with rightwards arrow on top. space straight d with rightwards arrow on top space equals space 15.

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202.

Let straight a with rightwards arrow on top space equals straight i with hat on top space minus straight j with hat on top comma space straight b with rightwards arrow on top space equals space 3 straight j with hat on top space minus space straight k with hat on top space and space straight c with rightwards arrow on top space equals 7 straight i with hat on top space minus space straight k with hat on top. Find a vector straight d with rightwards arrow on top which is perpendicular to both straight a with rightwards arrow on top space and space straight b with rightwards arrow on top and straight c with rightwards arrow on top. straight d with rightwards arrow on top space equals space 1

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203. Dot product of a vector with vectors 2 straight i with hat on top space plus space 3 straight j with hat on top space plus space straight k with hat on top comma space space 4 straight i with hat on top space plus space straight j with hat on top space and space straight i with hat on top space minus space 3 straight j with hat on top space minus space 7 straight k with hat on top are respectively 9, 7 and 6. Find the vector.
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 Multiple Choice QuestionsShort Answer Type

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204. Dot product of a vector with vectors 3 space straight i with hat on top minus 5 space straight k with hat on top comma space space space 2 straight i with hat on top plus space 7 space straight j with hat on top space and space straight i with hat on top plus straight j with hat on top plus straight k with hat on top are respectively – 1, 6 and 5. Find the vector.


Let straight r with rightwards arrow on top space equals space straight x straight i with hat on top space plus space straight y straight j with hat on top plus straight z straight k with hat on top be required vector.
From given conditions,
            left parenthesis straight x straight i with hat on top plus straight y straight j with hat on top plus straight z straight k with hat on top right parenthesis. space left parenthesis 3 straight i with hat on top space minus 5 straight k with hat on top right parenthesis space equals space minus 1 space space space space space space space rightwards double arrow space space space 3 straight x minus 5 straight z space equals space minus 1         ...(1)
            left parenthesis straight x straight i with hat on top plus straight y straight j with hat on top plus straight z straight k with hat on top right parenthesis. space left parenthesis 2 straight i with hat on top plus 7 straight j with hat on top right parenthesis space equals space 6 space space space rightwards double arrow space space space 2 straight x plus 7 straight y space equals space 6                       ...(2)
            left parenthesis straight x straight i with hat on top plus straight y straight j with hat on top plus straight z straight k with hat on top right parenthesis. space left parenthesis straight i with hat on top plus straight j with hat on top plus straight k with hat on top right parenthesis space equals space 5 space space space rightwards double arrow space space space straight x plus straight y plus straight z space equals space 5                     ...(3)
        7 space cross times space left parenthesis 3 right parenthesis space minus space left parenthesis 2 right parenthesis space gives comma space       5 straight x plus 7 straight z space equals 29                                          ...(4)
Multiplying (2) by 7 and (4) by 5, we get,
         21 x - 35 z = -7 
          25 x+35 z = 145
Adding these equation, 46x = 138  rightwards double arrow space space straight x space equals space 3
therefore space space from space left parenthesis 2 right parenthesis comma space 6 plus 7 straight y space equals space 6 space space space space rightwards double arrow space space space 7 straight y space equals space 0 space space space space rightwards double arrow space space straight y space equals space 0
From space left parenthesis 1 right parenthesis comma space space 9 space minus space 5 straight z space equals space minus 1 space space space space rightwards double arrow space space space minus 5 straight z space equals space minus 10 space rightwards double arrow space straight z space equals space 2
therefore space space space space straight r with rightwards arrow on top space equals space 3 straight i with hat on top plus 2 straight k with hat on top


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 Multiple Choice QuestionsLong Answer Type

205. Find the scalar components of a unit vector which is perpendicular to the vectors straight i with hat on top plus 2 space straight j with hat on top space minus space straight k with hat on top space space and space space 3 straight i with hat on top minus straight j with hat on top plus 2 space straight k with hat on top.
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 Multiple Choice QuestionsShort Answer Type

206.

If straight a with rightwards arrow on top plus straight b with rightwards arrow on top plus straight c with rightwards arrow on top space equals space 0 with rightwards arrow on top comma show that the angle straight theta between the vectors straight b with rightwards arrow on top space and space straight c with rightwards arrow on top is given by
cos space straight theta space equals space fraction numerator straight a squared minus straight b squared minus straight c squared over denominator 2 space open vertical bar straight b with rightwards arrow on top close vertical bar space open vertical bar straight c with rightwards arrow on top close vertical bar end fraction

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207.

If straight a with rightwards arrow on top plus straight b with rightwards arrow on top plus straight c with rightwards arrow on top space equals 0 with rightwards arrow on top space and space open vertical bar straight a with rightwards arrow on top close vertical bar space equals space 3 comma space space space open vertical bar straight b with rightwards arrow on top close vertical bar space equals space 5 comma space space open vertical bar straight c with rightwards arrow on top close vertical bar space equals 7 comma show that the angle between straight a with rightwards arrow on top space and space straight b with rightwards arrow on top is 60°.

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208.

Let straight a with rightwards arrow on top comma space straight b with rightwards arrow on top comma space straight c with rightwards arrow on top be three vectors of magnitude 5, 3, 1 respectively. If each one is perpendicular to the sum of other two vectors, prove that open vertical bar straight a with rightwards arrow on top plus straight b with rightwards arrow on top plus straight c with rightwards arrow on top close vertical bar space equals space square root of 35.

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209.

If straight a with rightwards arrow on top comma space straight b with rightwards arrow on top space and space straight c with rightwards arrow on top are three mutually perpendicular vectors of equal magnitude find the angle between straight a with rightwards arrow on top space and space left parenthesis straight a with rightwards arrow on top plus straight b with rightwards arrow on top plus straight c with rightwards arrow on top right parenthesis.

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 Multiple Choice QuestionsLong Answer Type

210.

If straight a with rightwards arrow on top comma space straight b with rightwards arrow on top space and space straight c with rightwards arrow on top are mutually perpendicular vectors of equal magnitude, show that they are equally inclined to the vector left parenthesis straight a with rightwards arrow on top plus straight b with rightwards arrow on top plus straight c with rightwards arrow on top right parenthesis

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