2.3.7. Vector Functions of a Real Variable
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Questions and Answers

What was a primary focus of the Soviet Union in the initial post-World War II years (1945-1953)?

  • Privatization of state-owned enterprises to encourage foreign investments.
  • Reconstruction prioritizing industry and agriculture. (correct)
  • Dismantling of the military forces and shifting resources to consumer goods production.
  • Rapid expansion of the service sector to improve living standards.

How did the Soviet Union's victory in World War II impact Stalin's authority?

  • It led to calls for democratization and decentralization of power.
  • It bolstered his prestige which led to a more dictatorial regime. (correct)
  • It weakened his position due to the immense human and economic costs.
  • It diminished because of criticism from allied nations.

Which of the following best describes the concept of an 'all-encompassing state' (Ολοκληρωτικό κράτος) as it relates to the Soviet Union under Stalin?

  • A state in which all power is concentrated in the hands of a single person, party or group. (correct)
  • A state where economic policies are determined by free market principles.
  • A state that promotes individual liberties and freedom of expression.
  • A state where power is distributed among different political parties.

What was a key characteristic of the Soviet economic system during the Stalin era?

<p>State control of production targets and economic sectors. (B)</p> Signup and view all the answers

What was a significant change initiated by Khrushchev after Stalin's death?

<p>The condemnation of Stalin's personality cult and some decentralization. (B)</p> Signup and view all the answers

What was a defining aspect of Khrushchev's foreign policy?

<p>Promotion of 'peaceful coexistence' and engagement with the West. (D)</p> Signup and view all the answers

Which of these actions is most representative of Khrushchev's efforts to improve living conditions in the Soviet Union?

<p>Investing significantly in housing construction. (A)</p> Signup and view all the answers

Which country's leader meeting with Khrushchev symbolized a practical move towards implementing the concept of 'peaceful coexistence'?

<p>John F. Kennedy of the United States (D)</p> Signup and view all the answers

What was a key focus of the Soviet Union's foreign policy during the Brezhnev era?

<p>Expanding its military influence and support for communist governments. (A)</p> Signup and view all the answers

How did the economic development of the Soviet Union change during the Brezhnev era compared to Khrushchev's time?

<p>The rate of economic growth slowed down, accompanied with stagnation. (D)</p> Signup and view all the answers

Flashcards

Totalitarian State

A state where one person, party, or group holds all power.

Peaceful coexistence

Theory advocating economic and political cooperation between countries with different systems.

De-Stalinization

Nikita Khrushchev condemned Stalin's cult of personality.

Reconstruction

The Soviet Union's focus after WWII

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Nikita Khrushchev

He succeeded Stalin, condemned his actions.

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Stalin

Developed the heavy industry but lowered living standards.

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Study Notes

Vector Functions of a Real Variable

  • A vector function of a real variable maps a real number to a vector in $R^n$.
  • Defined as $\mathbf{r}: I \subseteq \mathbb{R} \rightarrow \mathbb{R}^{n}$, where for each real number $t$ in the interval $I$, $\mathbf{r}(t)$ is a vector in $\mathbb{R}^{n}$.
  • $\mathbf{r}(t)$ can be expressed as $\mathbf{r}(t)=\left(f_{1}(t), f_{2}(t), \ldots, f_{n}(t)\right)$, where $f_{i}: I \subseteq \mathbb{R} \rightarrow \mathbb{R}$ are real-valued functions.

Trajectory of a Vector Function

  • The trajectory of a vector function is the set of all points $\mathbf{r}(t)$ in $\mathbb{R}^{n}$, for all $t$ in the domain of $\mathbf{r}$.
  • It represents the curve traced by the tip of the vector $\mathbf{r}(t)$ as $t$ varies.

Example Vector Function 1

  • Function: $\mathbf{r}(t)=2 \cos (t) \mathbf{i}+2 \operatorname{sen}(t) \mathbf{j}, \quad 0 \leq t \leq 2 \pi$
  • Parametric equations: $x=2 \cos (t)$ and $y=2 \operatorname{sen}(t)$
  • The functions satisfy the equation $x^{2}+y^{2}=4$.
  • The curve traced is a a circle of radius 2 centered at the origin

Example Vector Function 2

  • Function: $\mathbf{r}(t)=\cos (t) \mathbf{i}+\operatorname{sen}(t) \mathbf{j}+t \mathbf{k}$
  • The $\mathbf{i}$ and $\mathbf{j}$ components define a circle in the xy-plane.
  • The $\mathbf{k}$ component ($z=t$) causes the curve to rise or descend as ( t ) increases.
  • The function results in a helical curve winding around the z-axis.

Direct Stress

  • Also known as simple stress.
  • Includes tension, compression, and shear stress.

Tension Stress

  • Stress caused by pulling forces.
  • Calculated as $\sigma = \dfrac{F}{A}$, where $\sigma$ is stress, $F$ is applied force, and $A$ is cross-sectional area.
  • Elongation is considered positive.

Compression Stress

  • Stress caused by pushing forces.
  • Calculated as $\sigma = \dfrac{F}{A}$, where $\sigma$ is stress, $F$ is applied force, and $A$ is cross-sectional area.
  • Deformation is considered negative.

Shear Stress

  • Stress caused by forces acting parallel to a member.
  • Calculated as $\tau = \dfrac{V}{A}$, where $\tau$ is shear stress, $V$ is shear force, and $A$ is the area.

Bearing Stress

  • Contact pressure between two bodies.
  • Calculated as $\sigma_b = \dfrac{F}{A_b}$, where $\sigma_b$ is bearing stress, $F$ is applied force, and $A_b$ is bearing area.
  • For a cylinder, ( A_b = t \cdot d ), with ( t ) being plate thickness and ( d ) being cylinder diameter.

Example Problem

  • A steel bar with a cross-sectional area of 4 $in^2$ is under a tensile force of 70,000 lbs.
  • Tensile stress is ( \sigma = \dfrac{F}{A} = \dfrac{70,000 \ lbs}{4 \ in^2} = 17,500 \ psi ).

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Description

A vector function of a real variable maps a real number to a vector. The trajectory is the set of all points r(t) in n-dimensional Euclidean space for all t in the domain of r. It represents the curve traced by the tip of the vector r(t) as t varies.

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