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Specialist Mathematics ยท Unit 3 ยท Vectors in two and three dimensions ยท Algebra of vectors in three dimensions

Use the scalar (dot) product. ๐’‚ โ‹… ๐’ƒ = |๐’‚||๐’ƒ| cos(๐œƒ) ( ๐‘Ž1 ๐‘Ž2 ๐‘Ž3) โ‹… ( ๐‘1 ๐‘2 ๐‘3) = ๐‘Ž1 ๐‘1 + ๐‘Ž2 ๐‘2 + ๐‘Ž3 ๐‘3

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Question 1

Calculate the angle between the vectors \(\mathbf{u} = \begin{pmatrix} 2 \\ 1 \\ 2 \end{pmatrix}\) and \(\mathbf{v} = \begin{pmatrix} 0 \\ 3 \\ 1 \end{pmatrix}\).

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Question 2

Two forces acting on a particle are represented by vectors ฮฑ = (2, โˆ’1, 3) and ฮฒ = (โˆ’3, 4, 1). a) Calculate the scalar product ฮฑ โ‹… ฮฒ using the component form. (1) b) Hence, use the scalar product to determine the angle between the two force vectors, to the nearest degree. (1)

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Question 3

Two forces act on a particle at the origin. Force $\vec{F}_1$ has magnitude $10$ N and acts in the direction of vector $(3, 0, 4)$. Force $\vec{F}_2$ has magnitude $5$ N and acts in the direction of vector $(0, 1, 0)$. Calculate the angle between the two force vectors, correct to the nearest degree.

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Question 4

Consider the vectors \(\mathbf{p} = \begin{pmatrix} 3 \\ -2 \\ 5 \end{pmatrix}\) and \(\mathbf{q} = \begin{pmatrix} 4 \\ 1 \\ -3 \end{pmatrix}\). a) Determine the value of \(\mathbf{p} \cdot \mathbf{q}\). (1 mark) b) Use your result from part a) to determine the angle \(\theta\) between vectors \(\mathbf{p}\) and \(\mathbf{q}\). Give your answer in degrees, correct to 2 decimal places. (2 marks)

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