The problem involves a 3D force vector $\mathbf{F}$ acting on a block, and the task is to determine several related quantities.

Let's break down each part of the problem:

Given Data:

• The magnitude of force $\mathbf{F} = 840 \, \text{N}$
• Coordinates:
  • Point $A$: (275 mm, 0, 400 mm)
  • Point $B$: (150 mm, 200 mm, 0 mm)
  • Point $O$: (250 mm, 175 mm, 0 mm)
• You need to find:
  1. The moment of the force about point $B$.
  2. The direction associated with the unit vector along the axis of the moment.
  3. The perpendicular distance from point $B$ to the line of action of the force.

Approach:

• (a) Moment of the force about point $B$: The moment of a force $\mathbf{F}$ about a point $B$ is given by: $\mathbf{M}_B = \mathbf{r}_{B/A} \times \mathbf{F}$ Where $\mathbf{r}_{B/A}$ is the position vector from point $B$ to point $A$, and $\mathbf{F}$ is the force vector.

  To find $\mathbf{r}_{B/A}$, we subtract the coordinates of $B$ from those of $A$.

• (b) Direction associated with the unit vector $\mathbf{\lambda}$: The unit vector along the axis of the moment can be obtained by normalizing the moment vector $\mathbf{M}_B$: $\mathbf{\lambda} = \frac{\mathbf{M}_B}{|\mathbf{M}_B|}$

• (c) Perpendicular distance from $B$ to the line of action of the force: The perpendicular distance $d$ is related to the magnitude of the moment and the force by: $d = \frac{|\mathbf{M}_B|}{|\mathbf{F}|}$

Now, I'll calculate the required quantities.### Results:

1. Moment of the force about point $B$: $\mathbf{M}_B = \left[ -19.21 \, \text{N·m}, -76.83 \, \text{N·m}, -32.41 \, \text{N·m} \right]$

2. Unit vector along the axis of the moment: $\mathbf{\lambda} = \left[ -0.224, -0.898, -0.379 \right]$

3. Perpendicular distance from point $B$ to the line of action of the force: $d = 0.102 \, \text{m} \, \text{(or 101.87 mm)}$

Would you like more detailed explanations or have any other questions?

Related Questions:

1. How is the position vector between two points calculated?
2. What does a cross product represent in the context of moments?
3. Why is the direction of the moment important in physical applications?
4. How can the unit vector be interpreted geometrically?
5. What are practical examples where perpendicular distance is relevant in force systems?

Tip: Always ensure the units are consistent when performing vector operations, especially in problems involving distances, forces, and moments.