Exam-Style Questions on Vectors

OABC is a parallelogram with O as origin. The position vector of A is \(a\) and the position vector of C is \(c\).

F is the mid-point of AB and the point E divides the line OC such that OE:EC = 2:1.

The point E also divides the line AD such that AE:ED = 3:2.

Find the following in terms of \(a\) and \(c\).

(a) \(\overrightarrow{OB}\)

(b) \(\overrightarrow{AC}\)

(c) \(\overrightarrow{AE}\)

(d) the position vector of F.

(e) \(\overrightarrow{AD}\)

(f) \(\overrightarrow{BD}\)

Worked Solution

(a) Shape \(A\) is translated to shape \(B\) using the vector \( \begin{pmatrix}m\\n\\ \end{pmatrix}\). What are the values of \(m\) and \(n\)?

(b) Vectors \(a, b, c, d\) and \(e\) are drawn on an isometric grid. Write each of the vectors \(c, d\) and \(e\) in terms of \(a\) and/or \(b\).

Worked Solution

ABCD is a quadrilateral. The points E, F, G and H are the midpoints of the sides of this quadrilateral.

Show that HG is parallel to EF.

Worked Solution

ABCDOE is a regular hexagon with O as origin. The position vector of A is \(a\) and the position vector of B is \(b\).

Find the following in terms of \(a\) and \(b\).

(a) \(\overrightarrow{BA}\)

(b) \(\overrightarrow{OE}\)

(c) the position vector of C.

If the sides of the hexagon are each of length 10cm calculate:

(d) the size of angle \(BCD\).

(e) the area of triangle \(BCD\).

(f) the length of the line from B to D.

(g) the area of the hexagon.

Worked Solution

Consider a triangle ABC where M is the midpoint of AB and F is the point on BC where BF:FC = 3:4.

(a) If \(\overrightarrow{AB}=b\) and \(\overrightarrow{AC}=c\) work out \(\overrightarrow{MF}\) in terms of \(b\) and \(c\) giving your answer in its simplest form.

(b) Use your answer to part (a) to explain whether MF is parallel to AC or not.

Worked Solution

The line \(L_1\) passes through the points A(3, 5, 1) and B(3, 6, 0).

(a) Show that \(AB=\begin{pmatrix} 0 \\ 1 \\ -1 \\ \end{pmatrix}\)

(b) Find a direction vector for \(L_1\)

(c) a vector equation for \(L_1\)

Another line \(L_2\) has equation \(\begin{pmatrix} 8 \\ 3 \\ -2 \\ \end{pmatrix} + t \begin{pmatrix} -1 \\ 1 \\ 0 \\ \end{pmatrix}\). The lines \(L_1\) and \(L_2\) intersect at the point P.

(d) Find the coordinates of P.

(e) Find a direction vector for \(L_2\).

(f) Hence, find the angle between \(L_1\) and \(L_2\).

Worked Solution

Consider two perpendicular vectors \(p\) and \(q\).

(a) Let \(r=p-q\). Draw a diagram to show what this relationship might look like.

(b) If \(p=\begin{pmatrix} 4 \\ 1 \\ -3 \\ \end{pmatrix}\) and \(q=\begin{pmatrix} 3 \\ n \\ -5 \\ \end{pmatrix}\), where \(n\in \mathbb Z\), find \(n\).

Worked Solution

In the parallelogram OABC two of the sides can be represented by vectors \(a\) and \(c\).

\( \overrightarrow{OA} = a \) and \( \overrightarrow{OC} = c \)

\( X \) is the midpoint of the line \( AC \).

\( OCD \) is a straight line such that \(OC:CD = k:1 \)

Given that \( \overrightarrow{XD} = 3c - \frac12 a \) find the value of \( k \).

Worked Solution

The line L is parallel to the vector \(\begin{pmatrix} 2 \\ 5 \\ \end{pmatrix} \),

(a) Find the gradient of the line L .

The line L passes through the point (11, 3).

(b) Write down the equation of the line L in the form \(y=ax+b\)

(c) Find a vector equation for the line L.

Worked Solution

(a) If A is the point (3,5) write down the position vector of A.

(b) If B is the point (6,9) find \(\mid\overrightarrow{AB} \mid\) the magnitude of \( \overrightarrow{AB}\).

The following diagram is not to scale.

\(O\) is the origin, \(\overrightarrow{OP}=p\) and = \(\overrightarrow{OQ}=q\).

\(OP\) is extended to \(R\) so that \(OP=PR\).

\(OQ\) is extended to \(S\) so that \(OQ=QS\).

(c) Write down \(\overrightarrow{RQ}\) in terms of \(p\) and \(q\).

(d) \(PS\) and \(RQ\) intersect at \(M\) and \(RM=2 MQ\).

Use vectors to find the ratio \(PM:PS\), showing all your working.

Worked Solution

In the diagram above (not drawn to scale) \(X\) is the point on \(AB\) such that \(AX:XB = 9:4\).

The position vector of \(A\) is \(3a\) and the position vector of \(B\) is \(3b\).

Find the value of \(k\) if \(\vec{OX} = k(4a + 9b)\) where \(k\) is a scalar quantity.

Worked Solution

George and Hugo like to fly model airplanes. On one day George's plane takes off from level ground and shortly after that Hugo's plane takes off.

The position of George’s plane \(s\) seconds after it takes off is given by \(\begin{pmatrix} 1 \\ 2 \\ 0 \\ \end{pmatrix} + s\begin{pmatrix} 5 \\ -2 \\ 6 \\ \end{pmatrix} \) where the distances are in metres.

(a) Find the speed of George’s plane to the nearest integer.

(b) Find the height of George’s plane after four seconds.

The position of Hugo’s airplane \(t\) seconds after it takes off is given by \(\begin{pmatrix} 4 \\ -4 \\ 0 \\ \end{pmatrix}+t\begin{pmatrix} 7 \\ -2 \\ 9 \\ \end{pmatrix} \) where the distances are in metres.

(c) Show that the paths of the planes are not perpendicular.

The two airplanes collide at the point \((46, -16, 54)\).

(d) How long after George’s plane takes off does Hugo’s plane take off ?

Worked Solution