Suppose an object has an initial velocity vi at time t; and later, at time t, has velocity vf. The fact that the velocity changes tells us that the object undergoes an acceleration during the time interval At = tft₁. From the definition of acceleration, ā Vf - Vi te-ti Δύ Δt 9

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Chapter1: Units, Trigonometry. And Vectors
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**Learning Goal:**

Suppose an object has an initial velocity \(\vec{v}_i\) at time \(t_i\) and later, at time \(t_f\), has velocity \(\vec{v}_f\). The fact that the velocity changes tells us that the object undergoes an acceleration during the time interval \(\Delta t = t_f - t_i\). From the definition of acceleration,

\[
\vec{a} = \frac{\vec{v}_f - \vec{v}_i}{t_f - t_i} = \frac{\Delta \vec{v}}{\Delta t},
\]

we see that the acceleration vector points in the same direction as the vector \(\Delta \vec{v}\). This vector is the change in the velocity \(\Delta \vec{v} = \vec{v}_f - \vec{v}_i\), so to know which way the acceleration vector points, we have to perform the vector subtraction \(\vec{v}_f - \vec{v}_i\). This Tactics Box shows how to use vector subtraction to find the acceleration vector.

**Figure Explanation:**

The figure illustrates two velocity vectors, \(\vec{v}_i\) and \(\vec{v}_f\). The initial velocity vector, \(\vec{v}_i\), is represented as an arrow pointing to the right with a specific angle. The final velocity vector, \(\vec{v}_f\), is shown as an arrow pointing further to the right at an upward angle. Both vectors originate from different points that are marked with black dots, indicating the positions of the object at the initial and final times. The change in velocity can be visualized as the difference in direction and length between \(\vec{v}_f\) and \(\vec{v}_i\).
Transcribed Image Text:**Learning Goal:** Suppose an object has an initial velocity \(\vec{v}_i\) at time \(t_i\) and later, at time \(t_f\), has velocity \(\vec{v}_f\). The fact that the velocity changes tells us that the object undergoes an acceleration during the time interval \(\Delta t = t_f - t_i\). From the definition of acceleration, \[ \vec{a} = \frac{\vec{v}_f - \vec{v}_i}{t_f - t_i} = \frac{\Delta \vec{v}}{\Delta t}, \] we see that the acceleration vector points in the same direction as the vector \(\Delta \vec{v}\). This vector is the change in the velocity \(\Delta \vec{v} = \vec{v}_f - \vec{v}_i\), so to know which way the acceleration vector points, we have to perform the vector subtraction \(\vec{v}_f - \vec{v}_i\). This Tactics Box shows how to use vector subtraction to find the acceleration vector. **Figure Explanation:** The figure illustrates two velocity vectors, \(\vec{v}_i\) and \(\vec{v}_f\). The initial velocity vector, \(\vec{v}_i\), is represented as an arrow pointing to the right with a specific angle. The final velocity vector, \(\vec{v}_f\), is shown as an arrow pointing further to the right at an upward angle. Both vectors originate from different points that are marked with black dots, indicating the positions of the object at the initial and final times. The change in velocity can be visualized as the difference in direction and length between \(\vec{v}_f\) and \(\vec{v}_i\).
**TACTICS BOX 4.1: Finding the Acceleration Vector**

To find the acceleration between velocity \( \vec{v}_i \) and velocity \( \vec{v}_f \) (Figure 1), follow these steps:

1. **Draw the Velocity Vectors**: Position the velocity vectors \( \vec{v}_i \) and \( \vec{v}_f \) with their tails together. 

   - **Diagram 1**: Shows vectors \( \vec{v}_i \) and \( \vec{v}_f \) positioned tail to tail.

2. **Draw the Change in Velocity Vector**: Draw a vector from the tip of \( \vec{v}_i \) to the tip of \( \vec{v}_f \). This vector is \( \Delta \vec{v} \), representing \( \vec{v}_f = \vec{v}_i + \Delta \vec{v} \).

   - **Diagram 2**: Illustrates the vector \( \Delta \vec{v} \) connecting the tips of \( \vec{v}_i \) and \( \vec{v}_f \), forming a triangle.

3. **Identify the Acceleration Vector**: Return to the original motion diagram, and draw a vector at the middle dot in the direction of \( \Delta \vec{v} \); label it \( \vec{a} \). This represents the average acceleration at the midpoint between \( \vec{v}_i \) and \( \vec{v}_f \).

   - **Diagram 3**: Displays the vector \( \vec{a} \) as an orange arrow indicating the direction and sense of change in velocity.

---

**Part A**

**Motion Diagram Explanation**:

A motion diagram is shown for an object moving along a curved path. The dots, separated by equal intervals, represent the object's position at three subsequent instants. The vectors \( \vec{v}_1 \) and \( \vec{v}_2 \) illustrate the object's average velocity for the first and second intervals.

**Instructions**:

Draw the vector \( -\vec{v}_1 \) and the acceleration vector \( \vec{a} \), which represents the change in average velocity over the total time interval.

- **Diagram**: Visual interface for selecting and drawing vectors, showing \( \vec{v}_1 \
Transcribed Image Text:**TACTICS BOX 4.1: Finding the Acceleration Vector** To find the acceleration between velocity \( \vec{v}_i \) and velocity \( \vec{v}_f \) (Figure 1), follow these steps: 1. **Draw the Velocity Vectors**: Position the velocity vectors \( \vec{v}_i \) and \( \vec{v}_f \) with their tails together. - **Diagram 1**: Shows vectors \( \vec{v}_i \) and \( \vec{v}_f \) positioned tail to tail. 2. **Draw the Change in Velocity Vector**: Draw a vector from the tip of \( \vec{v}_i \) to the tip of \( \vec{v}_f \). This vector is \( \Delta \vec{v} \), representing \( \vec{v}_f = \vec{v}_i + \Delta \vec{v} \). - **Diagram 2**: Illustrates the vector \( \Delta \vec{v} \) connecting the tips of \( \vec{v}_i \) and \( \vec{v}_f \), forming a triangle. 3. **Identify the Acceleration Vector**: Return to the original motion diagram, and draw a vector at the middle dot in the direction of \( \Delta \vec{v} \); label it \( \vec{a} \). This represents the average acceleration at the midpoint between \( \vec{v}_i \) and \( \vec{v}_f \). - **Diagram 3**: Displays the vector \( \vec{a} \) as an orange arrow indicating the direction and sense of change in velocity. --- **Part A** **Motion Diagram Explanation**: A motion diagram is shown for an object moving along a curved path. The dots, separated by equal intervals, represent the object's position at three subsequent instants. The vectors \( \vec{v}_1 \) and \( \vec{v}_2 \) illustrate the object's average velocity for the first and second intervals. **Instructions**: Draw the vector \( -\vec{v}_1 \) and the acceleration vector \( \vec{a} \), which represents the change in average velocity over the total time interval. - **Diagram**: Visual interface for selecting and drawing vectors, showing \( \vec{v}_1 \
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