LFM Pure and Mechanics

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gaokao 2018 Q4 5 marks Dot Product Computation View
Given vectors $\boldsymbol { a } , \boldsymbol { b }$ satisfying $| \boldsymbol { a } | = 1 , \boldsymbol { a } \cdot \boldsymbol { b } = - 1$, then $\boldsymbol { a } \cdot ( 2 \boldsymbol { a } - \boldsymbol { b } ) =$
A. 4
B. 3
C. 2
D. 0
In $\triangle A B C$, $A D$ is the median to side $B C$, and $E$ is the midpoint of $A D$. Then $\overrightarrow { E B } =$
A. $\frac { 3 } { 4 } \overrightarrow { A B } - \frac { 1 } { 4 } \overrightarrow { A C }$
B. $\frac { 1 } { 4 } \overrightarrow { A B } - \frac { 3 } { 4 } \overrightarrow { A C }$
C. $\frac { 3 } { 4 } \overrightarrow { A B } + \frac { 1 } { 4 } \overrightarrow { A C }$
D. $\frac { 1 } { 4 } \overrightarrow { A B } + \frac { 3 } { 4 } \overrightarrow { A C }$
In $\triangle A B C$, $AD$ is the median to side $BC$, and $E$ is the midpoint of $AD$. Then $\overrightarrow { E B } =$
A. $\frac { 3 } { 4 } \overrightarrow { A B } - \frac { 1 } { 4 } \overrightarrow { A C }$
B. $\frac { 1 } { 4 } \overrightarrow { A B } + \frac { 3 } { 4 } \overrightarrow { A C }$
C. $\frac { 3 } { 4 } \overrightarrow { A B } + \frac { 1 } { 4 } \overrightarrow { A C }$
D. $\frac { 1 } { 4 } \overrightarrow { A B } + \frac { 3 } { 4 } \overrightarrow { A C }$
gaokao 2018 Q13 5 marks Perpendicularity or Parallel Condition View
Given vectors $a = ( 1,2 ) , b = ( 2 , - 2 ) , c = ( 1 , \lambda )$. If $c \parallel ( 2a + b )$, then $\lambda = $ $\_\_\_\_$.
gaokao 2019 Q3 5 marks Dot Product Computation View
Given $\overrightarrow { A B } = ( 2,3 ) , \overrightarrow { A C } = ( 3 , t ) , | \overrightarrow { B C } | = 1$, then $\overrightarrow { A B } \cdot \overrightarrow { B C } =$
A. - 3
B. - 2
C. 2
D. 3
gaokao 2019 Q7 5 marks Angle or Cosine Between Vectors View
Let points $A , B , C$ be non-collinear. Then ``the angle between $\overrightarrow { A B }$ and $\overrightarrow { A C }$ is acute'' is ``$| \overrightarrow { A B } + \overrightarrow { A C } | > | \overrightarrow { B C } |$'' a (A) sufficient but not necessary condition (B) necessary but not sufficient condition (C) necessary and sufficient condition (D) neither sufficient nor necessary condition
7. Given non-zero vectors $a , b$ satisfying $| a | = 2 | b |$ and $( a - b ) \perp b$, the angle between $a$ and $b$ is
A. $\frac { \pi } { 6 }$
B. $\frac { \pi } { 3 }$
C. $\frac { 2 \pi } { 3 }$
D. $\frac { 5 \pi } { 6 }$
7. Given non-zero vectors $\boldsymbol { a } , \boldsymbol { b }$ satisfying $| \boldsymbol { a } | = 2 | \boldsymbol { b } |$ and $( \boldsymbol { a } - \boldsymbol { b } ) \perp \boldsymbol { b }$ , the angle between $\boldsymbol { a }$ and $\boldsymbol { b }$ is
A. $\frac { \pi } { 6 }$
B. $\frac { \pi } { 3 }$
C. $\frac { 2 \pi } { 3 }$
D. $\frac { 5 \pi } { 6 }$
8. Two unit vectors $e _ { 1 } , e _ { 2 }$ have an angle of $60 ^ { \circ }$ between them. Vector $m = t e _ { 1 } + 2 e _ { 2 } ( t < 0 )$. Then
A. The maximum value of $\frac { | m | } { t }$ is $\frac { \sqrt { 3 } } { 2 }$
B. The minimum value of $\frac { | m | } { t }$ is $- 2$
C. The minimum value of $\frac { | m | } { t }$ is $\frac { \sqrt { 3 } } { 2 }$
D. The maximum value of $\frac { | m | } { t }$ is $- 2$
gaokao 2019 Q13 5 marks Angle or Cosine Between Vectors View
Given that $\boldsymbol { a } , \boldsymbol { b }$ are unit vectors and $\boldsymbol { a } \cdot \boldsymbol { b } = 0$ , if $\boldsymbol { c } = 2 \boldsymbol { a } - \sqrt { 5 } \boldsymbol { b }$ , then $\cos \langle \boldsymbol { a } , \boldsymbol { c } \rangle =$ \_\_\_\_\_\_.
13. Given vectors $\boldsymbol { a } = ( 2,2 ) , \boldsymbol { b } = ( - 8,6 )$ , then $\cos \langle \boldsymbol { a } , \boldsymbol { b } \rangle =$
13. Given that $\boldsymbol { a } , \boldsymbol { b }$ are unit vectors and $\boldsymbol { a } \cdot \boldsymbol { b } = 0$ , if $\boldsymbol { c } = 2 \boldsymbol { a } - \sqrt { 5 } \boldsymbol { b }$ , then $\cos \langle \boldsymbol { a } , \boldsymbol { c } \rangle =$ $\_\_\_\_$ .
gaokao 2020 Q6 5 marks Angle or Cosine Between Vectors View
Given vectors $\boldsymbol { a } , \boldsymbol { b }$ satisfying $| \boldsymbol { a } | = 5 , | \boldsymbol { b } | = 6 , \boldsymbol { a } \cdot \boldsymbol { b } = - 6$ , then $\cos \langle \boldsymbol { a } , \boldsymbol { a } + \boldsymbol { b } \rangle =$
A. $- \frac { 31 } { 35 }$
B. $- \frac { 19 } { 35 }$
C. $\frac { 17 } { 35 }$
D. $\frac { 19 } { 35 }$
Given vectors $\overrightarrow { a _ { 1 } } , \overrightarrow { a _ { 2 } } , \overrightarrow { b _ { 1 } } , \overrightarrow { b _ { 2 } } , \ldots , \overrightarrow { b _ { k } } \left( k \in \mathbb{N} ^ { * } \right)$ that are pairwise non-parallel in the plane, satisfying $\left| \overrightarrow { a _ { 1 } } - \overrightarrow { a _ { 2 } } \right| = 1$ and $\left| \overrightarrow { a _ { i } } - \overrightarrow { b _ { j } } \right| \in \{ 1,2 \}$ (where $i = 1,2$ and $j = 1,2 , \ldots , k$), find the maximum value of $k$ as $\_\_\_\_$
gaokao 2020 Q13 5 marks Perpendicularity or Parallel Condition View
Given unit vectors $\boldsymbol { a } , \boldsymbol { b }$ with an angle of $45 ^ { \circ }$ between them, and $k \boldsymbol { a } - \boldsymbol { b}$ is perpendicular to $\boldsymbol { a }$ , then $k = $ $\_\_\_\_$.
gaokao 2020 Q14 5 marks Perpendicularity or Parallel Condition View
Let vectors $\boldsymbol { a } = ( 1 , - 1 ) , \boldsymbol { b } = ( m + 1,2 m - 4 )$ . If $\boldsymbol { a } \perp \boldsymbol { b }$ , then $m =$ $\_\_\_\_$.
10. AC
Solution: $\left| \overrightarrow { O P _ { 1 } } \right| = \left| \overrightarrow { O P _ { 2 } } \right| = 1$, so A is correct; $\left| \overrightarrow { A P _ { 1 } } \right| ^ { 2 } = 2 - 2 \cos \alpha , \left| \overrightarrow { A P _ { 2 } } \right| ^ { 2 } = 2 - 2 \cos \beta$, so B is incorrect; $\overrightarrow { O P _ { 1 } } \cdot \overrightarrow { O P _ { 2 } } \sin \alpha \sin \beta = \cos ( \alpha + \beta ) = \overrightarrow { O A } \cdot \overrightarrow { O P _ { 3 } }$, so C is correct; $\overrightarrow { O P _ { 2 } } \cdot \overrightarrow { O P _ { 3 } } = \cos ( \alpha + \beta ) \cos \beta - \sin ( \alpha + \beta ) \sin \beta \neq \overrightarrow { O P _ { 1 } } = \cos \alpha$, so D is incorrect. The answer is $AC$.
gaokao 2021 Q13 Magnitude of Vector Expression View
13. If vectors $\vec { a } , \vec { b }$ satisfy $| \vec { a } | = 3 , | \vec { a } - \vec { b } | = 5 , \vec { a } \cdot \vec { b } = 1$, then $| \vec { b } | =$ $\_\_\_\_$ .
14. Given vectors $\vec{a} = (3,1)$, $\vec{b} = (1,0)$, $\vec{c} = \vec{a} + k\vec{b}$. If $\vec{a} \perp \vec{c}$, then $k = \_\_\_\_$.
gaokao 2022 Q3 5 marks Magnitude of Vector Expression View
Given vectors $a = ( 2,1 ) , b = ( - 2,4 )$ , then $| a - b | =$
A. 2
B. 3
C. 4
D. 5
gaokao 2022 Q3 5 marks Dot Product Computation View
Given vectors $\boldsymbol{a}, \boldsymbol{b}$ satisfy $|\boldsymbol{a}| = 1, |\boldsymbol{b}| = \sqrt{3}, |\boldsymbol{a} - 2\boldsymbol{b}| = 3$, then $\boldsymbol{a} \cdot \boldsymbol{b} =$
A. $-2$
B. $-1$
C. $1$
D. $2$
3. In $\triangle A B C$, point $D$ is on side $A B$ with $B D = 2 D A$. Let $\overrightarrow { C A } = m$ and $\overrightarrow { C D } = n$. Then $\overrightarrow { C B } =$
A. $3 m - 2 n$
B. $- 2 m + 3 n$
C. $3 \boldsymbol { m } + 2 \boldsymbol { n }$
D. $2 m + 3 n$
gaokao 2022 Q13 5 marks Perpendicularity or Parallel Condition View
Given vectors $\boldsymbol { a } = ( m , 3 ) , \boldsymbol { b } = ( 1 , m + 1 )$ . If $\boldsymbol { a } \perp \boldsymbol { b }$ , then $m =$ $\_\_\_\_$ .
gaokao 2022 Q13 5 marks Dot Product Computation View
Let vectors $\boldsymbol { a }$ and $\boldsymbol { b }$ have an angle whose cosine is $\frac { 1 } { 3 }$, and $| \boldsymbol { a } | = 1$, $| \boldsymbol { b } | = 3$. Then $( 2 \boldsymbol { a } + \boldsymbol { b } ) \cdot \boldsymbol { b } =$ $\_\_\_\_$
gaokao 2023 Q4 5 marks Angle or Cosine Between Vectors View
Vectors $|\boldsymbol{a}| = |\boldsymbol{b}| = 1 , |\boldsymbol{c}| = \sqrt{2}$ and $\boldsymbol{a} + \boldsymbol{b} + \boldsymbol{c} = 0$ , then $\cos \langle \boldsymbol{a} - \boldsymbol{b} , \boldsymbol{b} - \boldsymbol{c} \rangle =$
A. $-\frac{1}{5}$
B. $-\frac{2}{5}$
C. $\frac{2}{5}$
D. $\frac{4}{5}$