3. Show that if a particle moves with constant speed, then the velocity and acceleration vectors are orthog- onal.

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Chapter1: Functions And Models
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### Exercise 3: Orthogonality of Velocity and Acceleration Vectors

**Problem Statement:**
Show that if a particle moves with constant speed, then the velocity and acceleration vectors are orthogonal.

**Explanation:**
To solve this problem, follow the steps below:

1. **Constant Speed:** 
   - A particle moving with constant speed means the magnitude of its velocity vector `|v|` is constant. 
   
2. **Velocity Vector:**
   - Denote the velocity vector by **v**. Since its speed is constant, the derivative of the speed (which is the magnitude of the velocity) with respect to time is zero:
     \[
     \frac{d}{dt} (\| \mathbf{v} \|) = 0
     \]
     
3. **Dot Product of the Velocity with Itself:**
   - Write the speed squared in terms of the dot product of the velocity vector with itself:
     \[
     \|\mathbf{v}\|^2 = \mathbf{v} \cdot \mathbf{v}
     \]
     
4. **Differentiate the Dot Product:**
   - Differentiate both sides of the equation with respect to time:
     \[
     \frac{d}{dt} (\mathbf{v} \cdot \mathbf{v}) = \frac{d}{dt} (\|\mathbf{v}\|^2)
     \]
     Since the right-hand side is zero (because the speed is constant):
     \[
     2 \mathbf{v} \cdot \frac{d\mathbf{v}}{dt} = 0
     \]
     Simplifying this gives:
     \[
     \mathbf{v} \cdot \mathbf{a} = 0
     \]
     where \(\mathbf{a} = \frac{d\mathbf{v}}{dt}\) is the acceleration vector.

5. **Conclusion:**
   - The result shows that the dot product of the velocity and acceleration vectors is zero:
     \(\mathbf{v} \cdot \mathbf{a} = 0\)
     This implies that the velocity and acceleration vectors are orthogonal.

Therefore, if a particle moves with constant speed, the velocity and acceleration vectors must be orthogonal (perpendicular) to each other.

---
Transcribed Image Text:--- ### Exercise 3: Orthogonality of Velocity and Acceleration Vectors **Problem Statement:** Show that if a particle moves with constant speed, then the velocity and acceleration vectors are orthogonal. **Explanation:** To solve this problem, follow the steps below: 1. **Constant Speed:** - A particle moving with constant speed means the magnitude of its velocity vector `|v|` is constant. 2. **Velocity Vector:** - Denote the velocity vector by **v**. Since its speed is constant, the derivative of the speed (which is the magnitude of the velocity) with respect to time is zero: \[ \frac{d}{dt} (\| \mathbf{v} \|) = 0 \] 3. **Dot Product of the Velocity with Itself:** - Write the speed squared in terms of the dot product of the velocity vector with itself: \[ \|\mathbf{v}\|^2 = \mathbf{v} \cdot \mathbf{v} \] 4. **Differentiate the Dot Product:** - Differentiate both sides of the equation with respect to time: \[ \frac{d}{dt} (\mathbf{v} \cdot \mathbf{v}) = \frac{d}{dt} (\|\mathbf{v}\|^2) \] Since the right-hand side is zero (because the speed is constant): \[ 2 \mathbf{v} \cdot \frac{d\mathbf{v}}{dt} = 0 \] Simplifying this gives: \[ \mathbf{v} \cdot \mathbf{a} = 0 \] where \(\mathbf{a} = \frac{d\mathbf{v}}{dt}\) is the acceleration vector. 5. **Conclusion:** - The result shows that the dot product of the velocity and acceleration vectors is zero: \(\mathbf{v} \cdot \mathbf{a} = 0\) This implies that the velocity and acceleration vectors are orthogonal. Therefore, if a particle moves with constant speed, the velocity and acceleration vectors must be orthogonal (perpendicular) to each other. ---
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