1
IIT-JEE 2007 Paper 2 Offline
MCQ (Single Correct Answer)
+3
-1

Let $$\vec{a}, \vec{b}, \vec{c}$$ be unit vectors such that $$\vec{a}+\vec{b}+\vec{c}=\overrightarrow{0}$$. Which one of the following is correct?

A
$$\vec{a} \times \vec{b}=\vec{b} \times \vec{c}=\vec{c} \times \vec{a}=\overrightarrow{0}$$
B
$$\vec{a} \times \vec{b}=\vec{b} \times \vec{c}=\vec{c} \times \vec{a} \neq \overrightarrow{0}$$
C
$$\vec{a} \times \vec{b}=\vec{b} \times \vec{c}=\vec{a} \times \vec{c} \neq \overrightarrow{0}$$
D
$$\vec{a} \times \vec{b}, \vec{b} \times \vec{c}, \vec{c} \times \vec{a}$$ are mutually perpendicular
2
IIT-JEE 2007 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

The number of distinct real values of $$\lambda$$, for which the vectors $$ - {\lambda ^2}\widehat i + \widehat j + \widehat k,\widehat i - {\lambda ^2}\widehat j + \widehat k$$ and $$\widehat i + \widehat j - {\lambda ^2}\widehat k$$ are coplanar, is :

A
zero
B
one
C
two
D
three
3
IIT-JEE 2007 Paper 1 Offline
MCQ (Single Correct Answer)
+3
-1

Let the vector $$\overrightarrow {PQ} ,\overrightarrow {QR} ,\overrightarrow {RS} ,\overrightarrow {ST} ,\overrightarrow {TU} $$ and $$\overrightarrow {UP} $$, represent the sides of a regular hexagon.

Statement 1 : $$\overrightarrow {PQ} \times \left( {\overrightarrow {RS} + \overrightarrow {ST} } \right) \ne \overrightarrow 0 $$

Statement 2 : $$\overrightarrow {PQ} \times \overrightarrow {RS} = \overrightarrow 0 $$ and $$\overrightarrow {PQ} \times \overrightarrow {ST} \ne \overrightarrow 0 $$

A
Statement 1 is True, Statement 2 is True, Statement 2 is a CORRECT explanation for Statement 1
B
Statement 1 is True, Statement 2 is True, Statement 2 is NOT a CORRECT explanation for Statement 1
C
Statement 1 is True, Statement 2 is False
D
Statement 1 is False, Statement 2 is True
4
IIT-JEE 2006
MCQ (Single Correct Answer)
+3
-0.75
Let $$\overrightarrow a = \widehat i + 2\widehat j + \widehat k,\,\overrightarrow b = \widehat i - \widehat j + \widehat k$$ and $$\overrightarrow c = \widehat i + \widehat j - \widehat k.$$ A vector in the plane of $$\overrightarrow a $$ and $$\overrightarrow b $$ whose projection on $$\overrightarrow c $$ is $${1 \over {\sqrt 3 }},$$ is
A
$$4\widehat i - \widehat j + 4\widehat k$$
B
$$3\widehat i + \widehat j - 3\widehat k$$
C
$$2\widehat i + \widehat j - 2\widehat k$$
D
$$4\widehat i + \widehat j - 4\widehat k$$

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