Physics: Vectors and Scalars

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Questions and Answers

What distinguishes a vector quantity from a scalar quantity?

  • A vector has only magnitude.
  • A vector is always greater than a scalar.
  • A vector includes direction. (correct)
  • A vector can be expressed in different units.

Which of the following is an example of a scalar quantity?

  • Displacement
  • Temperature (correct)
  • Force
  • Velocity

Which operation is typically used for combining scalar quantities?

  • Cross product
  • Ordinary arithmetic (correct)
  • Geometric mean
  • Vector addition

In which coordinate system are the axes perpendicular and intersect at the origin?

<p>Cartesian coordinate system (A)</p> Signup and view all the answers

What must be described to provide a complete understanding of displacement?

<p>Both distance and direction (B)</p> Signup and view all the answers

What describes the Push or pull exerted on a body in physics?

<p>Force (C)</p> Signup and view all the answers

If an airplane travels 5 km east and then 5 km west, what is its net displacement?

<p>0 km (C)</p> Signup and view all the answers

Which of the following quantities can be considered a vector?

<p>Velocity (D)</p> Signup and view all the answers

What are the Cartesian coordinates for the given polar coordinates r = 5.5m and θ = 240°?

<p>x = -2.75 m, y = -4.76 m (B)</p> Signup and view all the answers

Under what condition can two vectors A and B be considered equal?

<p>They must have the same magnitude and point in the same direction. (C)</p> Signup and view all the answers

What is the resultant vector R when adding vectors A and B graphically?

<p>The vector drawn from the tail of A to the tip of B. (D)</p> Signup and view all the answers

What does the commutative law of addition state about vector addition?

<p>The sum is independent of the order of the addition of the vectors. (C)</p> Signup and view all the answers

In the context of vector addition, what is the 'head to tail method'?

<p>A method that involves positioning the tail of one vector at the head of another. (C)</p> Signup and view all the answers

How can vectors be added using a geometric construction?

<p>By completing a geometric figure to find the resultant. (A)</p> Signup and view all the answers

Which of the following statements is true regarding physical quantities represented by vectors?

<p>Vectors can represent both magnitude and direction. (C)</p> Signup and view all the answers

What is the method of vector addition that involves drawing vectors to scale on graph paper?

<p>The graphical method. (D)</p> Signup and view all the answers

What is the Associative Property of Addition in relation to vectors?

<p>The sum is independent of how vectors are grouped. (D)</p> Signup and view all the answers

Why is it meaningless to add a velocity vector to a displacement vector?

<p>They represent different physical quantities. (B)</p> Signup and view all the answers

What is the outcome when a vector is added to its negative?

<p>The result is zero for the vector sum. (A)</p> Signup and view all the answers

How is vector subtraction defined?

<p>As the addition of the first vector to the negative of the second vector. (A)</p> Signup and view all the answers

What does multiplying a vector by a scalar do to the vector's magnitude?

<p>It increases or decreases the magnitude based on the scalar. (A)</p> Signup and view all the answers

What must be true for two or more vectors to be added?

<p>They must all have the same units. (B)</p> Signup and view all the answers

When subtracting two vectors, how can you visualize the result geometrically?

<p>It points from the tip of the second vector to the tip of the first vector. (B)</p> Signup and view all the answers

Which statement accurately reflects the characteristics of negative vectors?

<p>Negative vectors have the same magnitude but point in opposite directions. (C)</p> Signup and view all the answers

What type of motion is exemplified by a car traveling on a highway?

<p>Translational (C)</p> Signup and view all the answers

In the particle model, how are we expected to treat the moving object?

<p>As a particle regardless of its size (B)</p> Signup and view all the answers

What is necessary to completely know the motion of a particle?

<p>Its position at all times (B)</p> Signup and view all the answers

When considering the motion of the Earth around the Sun, how is the Earth treated in the particle model?

<p>As a point-like object (C)</p> Signup and view all the answers

Which type of motion is described by a back-and-forth movement, such as a pendulum?

<p>Vibrational (A)</p> Signup and view all the answers

What serves as the reference point when collecting position data for a moving object?

<p>A fixed location that serves as the origin (A)</p> Signup and view all the answers

When analyzing motion in one dimension, which of the following is NOT considered a type of motion?

<p>Rotational (A)</p> Signup and view all the answers

What is a particle in the context of physics?

<p>A point-like object that has mass but is of infinitesimal size (A)</p> Signup and view all the answers

What describes the relationship between a vector's magnitude and its components?

<p>The magnitude is the hypotenuse of a right triangle formed by the components. (A)</p> Signup and view all the answers

How does the angle θ affect the components Ax and Ay?

<p>The signs of Ax and Ay depend on the specific angle value of θ. (B)</p> Signup and view all the answers

What is the definition of a unit vector?

<p>A vector with a magnitude of exactly 1 used to indicate direction. (B)</p> Signup and view all the answers

What notation is used to express a vector 𝑨⃗ in the xy-plane?

<p>𝑨⃗ = 𝐴 𝒊 + 𝐴 𝒋 (B)</p> Signup and view all the answers

What determines the signs of components Ax and Ay in a vector?

<p>The signs depend on the quadrant in which the vector lies. (D)</p> Signup and view all the answers

What are the symbols used to represent unit vectors in the positive x, y, and z directions?

<p>i, j, k (B)</p> Signup and view all the answers

What is the relationship between the angle θ and the vector components when θ = 120°?

<p>Ax is negative and Ay is positive. (B)</p> Signup and view all the answers

What can be said about the magnitude of unit vectors i, j, and k?

<p>They all have a magnitude of exactly 1. (D)</p> Signup and view all the answers

What is the x component of the hiker's displacement for the first day?

<p>17.68 km (A)</p> Signup and view all the answers

If a point has polar coordinates (5.50 m, 240°), what is its y coordinate in Cartesian coordinates?

<p>-4.15 m (A)</p> Signup and view all the answers

Which of the following quantities is not a vector?

<p>Temperature (C)</p> Signup and view all the answers

What is the total distance the hiker walked over the two days?

<p>65.0 km (C)</p> Signup and view all the answers

What can be concluded about the x component of a velocity vector pointing into the second quadrant?

<p>It is negative (C)</p> Signup and view all the answers

For a book moved around the perimeter of a 1.0 m x 2.0 m tabletop and returning to its initial position, what is its displacement?

<p>0 m (A)</p> Signup and view all the answers

What is the resultant displacement vector from the trip expressed in unit vectors?

<p>$R = 5.0 \hat{i} + 10.0 \hat{j}$ (C)</p> Signup and view all the answers

In terms of quadrants, what can be concluded about the vector $B - A$ if vector $A$ points into the second quadrant and vector $B$ points into the fourth quadrant?

<p>It cannot be in the first quadrant (D)</p> Signup and view all the answers

Flashcards

Scalar quantity

A physical quantity described by a single number and a unit, without a direction.

Vector quantity

A physical quantity that has both magnitude (size) and direction.

Velocity

Speed in a specific direction.

Displacement

Change in position of an object, a vector quantity.

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Cartesian coordinate system

A system used to describe locations in two dimensions using perpendicular axes.

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Origin

The point where the perpendicular axes intersect in a Cartesian coordinate system.

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Magnitude

The size or extent of something.

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Two-dimensional

Describing locations using two axes.

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Polar Coordinates

A coordinate system that represents a point using a distance from a reference point and an angle from a reference direction.

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Cartesian Coordinates

A coordinate system that represents a point using distances along perpendicular axes.

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Adding Vectors (Graphical)

Place the tail of one vector at the tip of another. The resultant vector starts at the tail of the first and ends at the tip of the second.

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Vector Addition (Polygon Method)

To add multiple vectors, draw them head-to-tail. The resultant vector goes from the tail of the first to the head of the last.

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Commutative Law of Vector Addition

The order in which vectors are added does not change the resultant vector.

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Resultant Vector

The vector that results from adding two or more vectors.

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Head-to-tail method

A method for adding vectors by placing the tail of one vector at the head of another.

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Associative Property of Addition (Vectors)

When adding three or more vectors, the sum is the same regardless of how the vectors are grouped.

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Vector Addition

Adding vectors with the same units and type.

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Negative of a Vector

A vector with the same magnitude but opposite direction.

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Vector Subtraction

Adding the negative of one vector to another.

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Multiplying a Vector by a Scalar

Multiplying or dividing a vector by a number to scale its magnitude, keeping the direction the same, if positive scalar

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Scalar

A quantity with only magnitude, no direction.

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Units of Vectors

Vectors must use consistent units (e.g., all velocities in km/hr, or all displacements in meters).

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Translational motion

Motion of an object along a straight line, changing its position from one point to another.

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Rotational motion

Motion of an object around a fixed axis, like a spinning top or the Earth around its axis.

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Vibrational motion

Back-and-forth motion of an object about a fixed point, like a pendulum swinging.

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Particle model

Describing a moving object as a point-like object, ignoring its size and internal structure.

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Reference point

A fixed position used as a starting point to describe the location of an object.

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Position

The location of an object relative to a chosen reference point.

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Coordinate system

A system used to describe locations in space by using numbers or coordinates.

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Hiker's displacement (Day 1)

The change in position of the hiker on the first day, represented as a vector with magnitude and direction. The hiker walks 25.0 km southeast.

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Hiker's displacement (Day 2)

The change in position of the hiker on the second day, represented as a vector with magnitude and direction. The hiker walks 40.0 km in a direction 60.0° north of east.

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Resultant displacement 𝑹⃗

The overall change in position of the hiker from the starting point to the final destination, represented as a vector.

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Components of displacement

These are the projections of a displacement vector onto the x-axis and y-axis, representing the horizontal and vertical changes in position.

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Unit vectors 𝒊̂ and 𝒋̂

Vectors with a magnitude of 1 that point in the direction of the x-axis and y-axis, respectively. They are used to represent directions.

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Displacement vs. distance

Displacement is the change in position, a vector quantity. Distance is the total length of the path traveled, a scalar quantity.

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Is force a vector?

Yes, force is a vector quantity. It has both magnitude and direction.

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Is the height of a building a vector?

No, the height of a building is a scalar quantity. It has only magnitude, no direction.

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Vector Components

A vector can be broken down into perpendicular parts called components. These components represent the vector's influence in each direction.

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Magnitude of Vector Components

The lengths of a vector's components are found using trigonometry. The hypotenuse of the right triangle is the vector's magnitude, and the components are the adjacent and opposite sides.

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Direction of Vector Components

The signs of the components (positive or negative) depend on the quadrant where the vector lies. For example, a vector in the second quadrant has a negative x-component and a positive y-component.

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Unit Vector

A vector with a magnitude of 1, used to represent a direction. The common unit vectors are i (x-direction), j (y-direction), and k (z-direction).

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Component Vector Notation

A vector can be expressed using unit vectors and its components. For example, a vector A in the xy plane is written as A = Axi + Ayj.

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Component Vector

A vector that represents a portion of a larger vector's influence in a specific direction. It is parallel to a coordinate axis and has a magnitude equal to the corresponding component of the original vector.

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Unit Vector Notation (xy plane)

A convenient way to represent a vector in the x-y plane using unit vectors i and j for the x and y directions respectively. This simplifies the representation to a linear combination of the components multiplied by the corresponding unit vectors.

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Study Notes

Vectors and Scalars

  • Physical quantities like time, temperature, mass, and density are described by a single number (scalar).
  • Other quantities, like velocity and force, have both a magnitude and a direction (vector).

Scalar Quantities

  • Described by magnitude alone.
  • Arithmetic operations are used for calculations.

Vector Quantities

  • Described by magnitude and direction.
  • Special operations are required for calculations.
  • Example: Velocity, Force.

Displacement

  • A vector quantity representing a change in position.
  • Magnitude and direction specify the displacement.
  • Example: Walking 3 km north is different from walking 3 km south-east.

Coordinate Systems

  • Cartesian (rectangular) coordinates: Two perpendicular axes (x and y) intersecting at the origin.

  • Polar coordinates: Distance (r) from the origin and angle (θ) from a reference axis.

  • Equations relating Cartesian and polar coordinates:

    • x = r cos θ
    • y = r sin θ
    • r = √(x² + y²)
    • θ = tan⁻¹(y/x)

Vector Properties

  • Equality: Vectors are equal if they have the same magnitude and direction, regardless of their starting points.
  • Commutative law of addition: The order of addition does not affect the result.
  • Associative law of addition: The grouping of vectors in addition does not affect the result.

Adding Vectors

  • Graphical method: Draw vectors with their tails connected. The resultant vector goes from the initial tail to the final tip.
  • Geometric (head-to-tail) method: Connect the tail of one vector to the head of the other. The resultant vector goes from the beginning of the first to the end of the last.

Subtracting Vectors

  • A-B = A + (-B)
  • Geometrically, find the vector that when added to B gives A.

Multiplying a Vector by a Scalar

  • Multiplying a vector by a scalar changes its magnitude but not its direction.
  • A scalar is a positive or negative number, which changes the magnitude; a positive scalar does not impact the direction of a vector.
  • A negative scalar changes the direction of the vector to the opposite direction.

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