Scalar triple product
With the dot product you measured angles and lengths; with the cross product, areas. To measure volumes in space you need to combine the two: the scalar triple product of three vectors, which at heart is nothing more than a $3\times3$ determinant.
Definition: the scalar triple product
Given the vectors $\vec{u} = (2, -1, 3)$, $\vec{v} = (0, 4, 1)$, and $\vec{w} = (1, 1, -2)$, calculate the value of the scalar triple product…
Given the vectors $\vec{u} = (2, -1, 3)$, $\vec{v} = (0, 4, 1)$, and $\vec{w} = (1, 1, -2)$, calculate the value of the scalar triple product $[\vec{u}, \vec{v}, \vec{w}]$ using the definition based on the determinant of their components.
The absolute value: volume of the parallelepiped
An engineering student is designing a component using CAD software. The base of the component is defined by the vectors $\vec{a} = (3, 0, 0)$ and $\vec{b} = (0, 5, 0)$,…
An engineering student is designing a component using CAD software. The base of the component is defined by the vectors $\vec{a} = (3, 0, 0)$ and $\vec{b} = (0, 5, 0)$, while the third vector defining the depth is $\vec{c} = (1, 2, 4)$. Calculate the volume of the parallelepiped formed by these three vectors.
Consider a storage hangar in the shape of a parallelepiped where three of its edges meeting at a vertex are the vectors $\vec{u} = (3, 0, 0)$, $\vec{v} = (0, 4, 0)$, and…
Consider a storage hangar in the shape of a parallelepiped where three of its edges meeting at a vertex are the vectors $\vec{u} = (3, 0, 0)$, $\vec{v} = (0, 4, 0)$, and $\vec{w} = (1, 2, 5)$.
- a) Calculate the total volume of the hangar.
- b) If the hangar is divided by an inclined plane passing through the endpoints of the three previous vectors to create a triangular mezzanine (tetrahedron with the origin), what fraction of the total volume of the hangar would this mezzanine occupy?
Coplanarity: when the volume is zero
Check, giving reasons, whether the vectors $\vec{a} = (1, 2, -1)$, $\vec{b} = (3, 0, 2)$, and $\vec{c} = (4, 2, 1)$ are coplanar. To do this, calculate their scalar…
Check, giving reasons, whether the vectors $\vec{a} = (1, 2, -1)$, $\vec{b} = (3, 0, 2)$, and $\vec{c} = (4, 2, 1)$ are coplanar. To do this, calculate their scalar triple product and justify your answer based on the result obtained.
Check whether the points $P(1, 2, -1)$, $Q(3, 0, 2)$, $R(2, 1, 4)$, and $S(5, -2, 7)$ are coplanar using the scalar triple product. If they are not, calculate the volume…
Check whether the points $P(1, 2, -1)$, $Q(3, 0, 2)$, $R(2, 1, 4)$, and $S(5, -2, 7)$ are coplanar using the scalar triple product. If they are not, calculate the volume of the tetrahedron that has these four points as vertices.
Properties of the scalar triple product
Given three linearly independent vectors $\vec{u}$, $\vec{v}$, and $\vec{w}$ such that their scalar triple product is $[\vec{u}, \vec{v}, \vec{w}] = 4$, calculate,…
Given three linearly independent vectors $\vec{u}$, $\vec{v}$, and $\vec{w}$ such that their scalar triple product is $[\vec{u}, \vec{v}, \vec{w}] = 4$, calculate, giving reasons and applying the properties of determinants, the value of the scalar triple product of the vectors $\vec{x} = 2\vec{u}$, $\vec{y} = \vec{u} + \vec{v}$, and $\vec{z} = \vec{w} - \vec{v}$.
Application: the volume of a tetrahedron
Given the vectors $\vec{u} = (1, 0, 1)$ and $\vec{v} = (2, 1, -1)$, find a third vector $\vec{w}$ of the form $(0, 0, z)$ such that the volume of the parallelepiped…
Given the vectors $\vec{u} = (1, 0, 1)$ and $\vec{v} = (2, 1, -1)$, find a third vector $\vec{w}$ of the form $(0, 0, z)$ such that the volume of the parallelepiped defined by the three is exactly 5 cubic units.
An architectural firm designs a skylight in the shape of a tetrahedron whose vertices are the points $A(1, 1, 1)$, $B(3, 2, 0)$, $C(2, 4, -1)$, and $D(0, 0, z)$.…
An architectural firm designs a skylight in the shape of a tetrahedron whose vertices are the points $A(1, 1, 1)$, $B(3, 2, 0)$, $C(2, 4, -1)$, and $D(0, 0, z)$. Calculate the value of the z-coordinate $z$ knowing that the volume of the skylight is $5$ cubic units and that vertex $D$ lies on the negative semi-axis of the $Z$.