Pac-Man undergoes a displacement [tex]\overrightarrow{\Delta r} = 2.0 \hat{i} - 3.0 \hat{j} + 6.0 \hat{k}[/tex], ending with the position vector [tex]\vec{r} = 3.0 \hat{j} - 4.0 \hat{k}[/tex], both measured in meters. What was Pac-Man's initial position vector?

[tex]
\vec{r}_i = r_x \hat{i} + r_y \hat{j} + r_z \hat{k}
[/tex]

[tex]r_x = [/tex]
A. Choose an answer [ ]
B. [ ]

[tex]r_y = [/tex]
C. Choose an answer [ ]
D. [ ]

[tex]r_z = [/tex]
Choose an answer [ ]
[ ]



Answer :

To determine Pac-Man's initial position vector, we'll start with the relation between the initial position vector [tex]\(\vec{r}_i\)[/tex], the displacement vector [tex]\(\overrightarrow{\Delta r}\)[/tex], and the final position vector [tex]\(\vec{r}_f\)[/tex]:

[tex]\[ \vec{r}_i + \overrightarrow{\Delta r} = \vec{r}_f \][/tex]

We can rearrange this equation to solve for the initial position vector, [tex]\(\vec{r}_i\)[/tex]:

[tex]\[ \vec{r}_i = \vec{r}_f - \overrightarrow{\Delta r} \][/tex]

Given:
- Displacement vector: [tex]\(\overrightarrow{\Delta r} = 2.0 \hat{i} - 3.0 \hat{j} + 6.0 \hat{k}\)[/tex]
- Final position vector: [tex]\(\vec{r}_f = 3.0 \hat{j} - 4.0 \hat{k}\)[/tex]

(Noting that the final position in the [tex]\(x\)[/tex]-direction is 0, we can write [tex]\(\vec{r}_f\)[/tex] as [tex]\(0 \hat{i} + 3.0 \hat{j} - 4.0 \hat{k}\)[/tex]).

We subtract the displacement vector from the final position vector component-wise:

[tex]\[ \vec{r}_i = \left(0 \hat{i} + 3.0 \hat{j} - 4.0 \hat{k}\right) - \left(2.0 \hat{i} - 3.0 \hat{j} + 6.0 \hat{k}\right) \][/tex]

This gives us individual components for [tex]\(\vec{r}_i\)[/tex]:

[tex]\[ r_x = 0 - 2.0 = -2.0 \][/tex]
[tex]\[ r_y = 3.0 - (-3.0) = 3.0 + 3.0 = 6.0 \][/tex]
[tex]\[ r_z = -4.0 - 6.0 = -10.0 \][/tex]

Therefore, Pac-Man's initial position vector is:

[tex]\[ \vec{r}_i = -2.0 \hat{i} + 6.0 \hat{j} - 10.0 \hat{k} \][/tex]

So, the initial position vector components are:
[tex]\[ r_x = -2.0, \quad r_y = 6.0, \quad r_z = -10.0 \][/tex]