Vector Cross Dot
1. The problem is to find the value of the vector expression $2\mathbf{i} \times 2\mathbf{j} \cdot \mathbf{k}$.
2. Recall the vector operations involved:
- The cross product $\times$ between two vectors results in a vector perpendicular to both.
- The dot product $\cdot$ between two vectors results in a scalar.
3. First, compute the cross product $2\mathbf{i} \times 2\mathbf{j}$:
$$2\mathbf{i} \times 2\mathbf{j} = 4 (\mathbf{i} \times \mathbf{j})$$
4. Using the right-hand rule and standard unit vectors:
$$\mathbf{i} \times \mathbf{j} = \mathbf{k}$$
5. Therefore:
$$4 (\mathbf{i} \times \mathbf{j}) = 4\mathbf{k}$$
6. Now compute the dot product of this result with $\mathbf{k}$:
$$4\mathbf{k} \cdot \mathbf{k} = 4 (\mathbf{k} \cdot \mathbf{k})$$
7. Since the dot product of a unit vector with itself is 1:
$$\mathbf{k} \cdot \mathbf{k} = 1$$
8. Hence:
$$4 (\mathbf{k} \cdot \mathbf{k}) = 4 \times 1 = 4$$
9. Final answer:
$$\boxed{4}$$