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Velocity and acceleration from position Consider the following position functions. a. Find the velocity and speed of the object. b. Find the acceleration of the object. $$\mathbf{r}(t)=\left\langle 3 t^{2}+1,4 t^{2}+3\right\rangle, \text { for } t \geq 0$$

Short Answer

Expert verified
Answer: The velocity vector is $$\mathbf{v}(t)=\left\langle6t,8t\right\rangle$$, the speed of the object is $$10t$$, and the acceleration vector is $$\mathbf{a}(t)=\left\langle6,8\right\rangle$$.

Step by step solution

01

Finding the velocity vector

Differentiate the position function vector with respect to time to find the velocity vector ($$\mathbf{v}(t)$$). In other words, find $$\frac{d}{dt}\mathbf{r}(t)$$. Given, $$\mathbf{r}(t)=\left\langle 3 t^{2}+1,4 t^{2}+3\right\rangle$$ Differentiate both components with respect to time: $$\mathbf{v}(t)=\frac{d}{dt}\mathbf{r}(t)=\left\langle\frac{d}{dt}(3t^2+1),\frac{d}{dt}(4t^2+3)\right\rangle$$ $$\mathbf{v}(t)=\left\langle6t,8t\right\rangle$$ So, the velocity vector is $$\mathbf{v}(t)=\left\langle6t,8t\right\rangle$$
02

Finding the speed of the object

To find the speed of the object, we will find the magnitude of the velocity vector. The formula for the magnitude of a vector is given by: $$\lVert\mathbf{v}\rVert=\sqrt{(v_1)^2+(v_2)^2}$$ For the given velocity vector, $$\mathbf{v}(t)=\left\langle6t,8t\right\rangle$$, we have: $$\lVert\mathbf{v}\rVert=\sqrt{(6t)^{2}+(8t)^{2}}=\sqrt{100t^2}=10t$$ So, the speed of the object is $$10t$$.
03

Finding the acceleration vector

Differentiate the velocity vector with respect to time to find the acceleration vector ($$\mathbf{a}(t)$$). In other words, find $$\frac{d}{dt}\mathbf{v}(t)$$. Given, $$\mathbf{v}(t)=\left\langle6t,8t\right\rangle$$ Differentiate both components with respect to time: $$\mathbf{a}(t)=\frac{d}{dt}\mathbf{v}(t)=\left\langle\frac{d}{dt}(6t),\frac{d}{dt}(8t)\right\rangle$$ $$\mathbf{a}(t)=\left\langle6,8\right\rangle$$ So, the acceleration vector is $$\mathbf{a}(t)=\left\langle6,8\right\rangle$$. In conclusion, the velocity vector is $$\mathbf{v}(t)=\left\langle6t,8t\right\rangle$$, the speed of the object is $$10t$$, and the acceleration vector is $$\mathbf{a}(t)=\left\langle6,8\right\rangle$$.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Position Vector
Understanding position vectors is crucial when dealing with motion problems. A position vector defines the specific location of an object in a coordinate space at a given time. It provides the "address" of the object within our environmental map, allowing us to track its movements. To break it down:
  • The position vector, often denoted as \( \mathbf{r}(t) \), is a function of time, \( t \).
  • It usually consists of two or three components (like \( \langle x(t), y(t), z(t) \rangle \)), each representing directional distances.
In the given exercise, the position vector \( \mathbf{r}(t)=\left\langle 3t^{2}+1, 4t^{2}+3 \right\rangle \) implies that both the \( x \)-coordinate and \( y \)-coordinate change with time. This continuous update enables one to determine where the object is located at any time \( t \). The coefficients of the \( t^2 \) terms reveal the path's curvature and how the object's position evolves.
Velocity Vector
Velocity vectors describe the rate of change of position over time, capturing how fast and in what direction an object is moving. Comprehending this allows for predictions of future positions if the velocity remains constant.Key points about the velocity vector:
  • Calculated by taking the derivative of the position vector components concerning time.
  • Denoted as \( \mathbf{v}(t) \), it shows both speed and direction.
In our exercise, differentiating \( \mathbf{r}(t)=\left\langle 3t^{2}+1, 4t^{2}+3 \right\rangle \) gives us \( \mathbf{v}(t)=\left\langle 6t, 8t \right\rangle \). This indicates that for every unit increase in time, the velocity changes linearly regarding \( t \), revealing the dynamic nature of motion in two-dimensional space.
Acceleration Vector
The acceleration vector addresses how an object's velocity changes over time, providing deeper insight into forces at play. It's essential for analyzing motion where speed or direction is not constant.Considerations for the acceleration vector:
  • Obtained by differentiating the velocity vector.
  • It tells us about the "push" or "pull" that modifies the current velocity.
By evaluating \( \mathbf{v}(t)=\left\langle 6t, 8t \right\rangle \), the acceleration vector \( \mathbf{a}(t)=\left\langle 6, 8 \right\rangle \) is derived. This constant vector indicates uniform acceleration, meaning the object's velocity components increase steadily at the rates of 6 and 8 units, respectively, in their directions. Understanding this uniform rate helps predict future velocity.
Differentiation
Differentiation is a mathematical process fundamental to calculus used to analyze changing quantities. It aids in determining rate changes, essential for understanding dynamic systems like motion.Why differentiation matters:
  • It converts position vectors into velocity vectors and velocity vectors into acceleration vectors.
  • Helps in identifying instantaneous rates of change.
In our task, differentiating \( \mathbf{r}(t) \) resulted in the velocity vector \( \mathbf{v}(t) \). Further differentiating \( \mathbf{v}(t) \) gave us the acceleration vector \( \mathbf{a}(t) \). This chain of differentiation enables the connection of position, velocity, and acceleration, revealing the full dynamics of an object's path. Mastery of differentiation empowers students to comprehend complex motion scenarios seamlessly.

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