1
IIT-JEE 1999
+2
-0.5
Let $$a=2i+j-2k$$ and $$b=i+j.$$ If $$c$$ is a vector such that $$a.$$ $$c = \left| c \right|,\left| {c - a} \right| = 2\sqrt 2$$ and the angle between $$\left( {a \times b} \right)$$ and $$c$$ is $${30^ \circ },$$ then $$\left| {\left( {a \times b} \right) \times c} \right| =$$
A
$$2/3$$
B
$$3/2$$
C
$$2$$
D
$$3$$
2
IIT-JEE 1999
+2
-0.5
Let $$a=2i+j+k, b=i+2j-k$$ and a unit vector $$c$$ be coplanar. If $$c$$ is perpendicular to $$a,$$ then $$c =$$
A
$${1 \over {\sqrt 2 }}\left( { - j + k} \right)$$
B
$${1 \over {\sqrt 3 }}\left( {- i - j - k} \right)$$
C
$${1 \over {\sqrt 5 }}\left( {i - 2j} \right)$$
D
$${1 \over {\sqrt 3 }}\left( {i - j - k} \right)$$
3
IIT-JEE 1998
+2
-0.5
If $$a = i + j + k,\overrightarrow b = 4i + 3j + 4k$$ and $$c = i + \alpha j + \beta k$$ are linearly dependent vectors and $$\left| c \right| = \sqrt 3 ,$$ then
A
$$\alpha = 1,\,\,\beta = - 1$$
B
$$\alpha = 1,\,\,\beta = \pm 1$$
C
$$\alpha = - 1,\,\,\beta = \pm 1$$
D
$$\alpha = \pm 1,\,\,\beta = 1$$
4
IIT-JEE 1998
+2
-0.5
For three vectors $$u,v,w$$ which of the following expression is not equal to any of the remaining three?
A
$$\,u \bullet \left( {v \times w} \right)$$
B
$$\left( {v \times w} \right) \bullet u$$
C
$$\,v \bullet \left( {u \times w} \right)$$
D
$$\left( {u \times v} \right) \bullet w$$
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