Chapter 13: Problem 14
In Exercises \(11-14,\) write a in the form \(\mathbf{a}=a_{\mathrm{T}} \mathbf{T}+a_{\mathrm{N}} \mathbf{N}\) at the given value of \(t\) without finding \(\mathbf{T}\) and \(\mathbf{N} .\) $$ \mathbf{r}(t)=\left(e^{t} \cos t\right) \mathbf{i}+\left(e^{t} \sin t\right) \mathbf{j}+\sqrt{2 e^{t} \mathbf{k},} \quad t=0 $$
Short Answer
Step by step solution
Find the Velocity Vector
Calculate Velocity Components
Evaluate Velocity at t=0
Find the Acceleration Vector
Calculate Acceleration Components
Evaluate Acceleration at t=0
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Velocity Vectors
For example, if an object moves in a 3D space, and its position is given by \( \mathbf{r}(t) = \left(e^{t} \cos t\right) \mathbf{i} + \left(e^{t} \sin t\right) \mathbf{j} + \sqrt{2e^{t}} \mathbf{k} \), the velocity vector at any time \( t \) is:
- The \( i \)-component: \( \frac{d}{dt} (e^{t} \cos t) \)
- The \( j \)-component: \( \frac{d}{dt} (e^{t} \sin t) \)
- The \( k \)-component: \( \frac{d}{dt} (\sqrt{2e^{t}}) \)
Delving into Acceleration Vectors
Acceleration consists of components along each coordinate axis:
- The \( i \)-component derives from differentiating the \( \mathbf{i} \) part of \( \mathbf{v}(t) \)
- The \( j \)-component involves differentiating the \( \mathbf{j} \) part
- The \( k \)-component involves differentiating the \( \mathbf{k} \) part
Exploring Position Vectors
To understand position in three dimensions, consider:
- The x-coordinate (e.g., \( e^{t} \cos t \)) gives the horizontal position.
- The y-coordinate (e.g., \( e^{t} \sin t \)) indicates vertical placement.
- The z-coordinate (e.g., \( \sqrt{2e^{t}} \)) reveals depth.
The Role of Differentiation
Consider the movement of an object whose position is given by \( \mathbf{r}(t) \). Differentiating once gives the velocity vector \( \mathbf{v}(t) \); differentiating again gives the acceleration \( \mathbf{a}(t) \). This process is fundamental because:
- Velocity reveals speed and direction dynamics.
- Acceleration shows how velocity changes, thus explaining dynamics of motion including speeding up and slowing down.