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Vectors and Vector Operations in Physics

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  • What is a vector in physics?

    A vector is a quantity that has both magnitude and direction, represented by an arrow.

  • What distinguishes a scalar from a vector?

    Scalars have only magnitude, while vectors have both magnitude and direction.

  • How is the magnitude of a vector represented?

    The magnitude of a vector 𝐴⃗ is denoted as 𝐴 and equals the length of the arrow, with the same units as the vector.

  • How is the direction of a 2D vector specified?

    By an angle 𝜃 relative to the positive x-axis, measured counterclockwise (positive) or clockwise (negative).

  • What are the formulas for the x- and y-components of a vector?

    𝐴ₓ = 𝐴 cos 𝜃 and 𝐴ᵧ = 𝐴 sin 𝜃, valid in all four quadrants.

  • How do you find the magnitude of a vector from its components?

    Use the Pythagorean theorem: \(A=\sqrt{A_x^2 + A_y^2}\).

  • How do you find the direction angle of a vector from its components?

    Use the inverse tangent: \(\theta=\arctan\left(\frac{A_y}{A_x}\right)\), adjusting for quadrant.

  • What is the tip-to-tail rule in vector addition?

    Place the tail of one vector at the tip of another; the resultant vector goes from the tail of the first to the tip of the second.

  • Is vector addition commutative?

    Yes, 𝐴⃗ + 𝐵⃗ = 𝐵⃗ + 𝐴⃗.

  • How is vector subtraction defined?

    𝐴⃗ - 𝐵⃗ = 𝐴⃗ + (-𝐵⃗), where -𝐵⃗ is the vector with the same magnitude but opposite direction as 𝐵⃗.

  • What is the component method for adding multiple vectors?

    Add all x-components and y-components separately, then find magnitude and direction of the resultant vector.

  • How is a vector represented in 3D Cartesian coordinates?

    As 𝐴⃗ = A_x 𝚤̂ + A_y 𝚥̂ + A_z 𝑘̂, with components along x, y, and z axes.

  • How do you find the magnitude of a 3D vector?

    Use \(A=\sqrt{A_x^2 + A_y^2 + A_z^2}\).

  • What is the scalar (dot) product of two vectors?

    𝑎⃗ ⋅ 𝑏⃗ = a_x b_x + a_y b_y + a_z b_z, resulting in a scalar.

  • What does the scalar product tell us about the angle between two vectors?

    \(\cos \theta = \frac{\mathbf{a} \cdot \mathbf{b}}{ab}\), where 𝜃 is the angle between vectors.

  • When is the scalar product zero, positive, or negative?

    Zero if vectors are perpendicular, positive if angle < 90°, negative if angle > 90°.

  • What is the vector (cross) product of two vectors?

    𝑐⃗ = 𝑎⃗ × 𝑏⃗ is a vector perpendicular to both 𝑎⃗ and 𝑏⃗, with magnitude \(c = ab \sin \theta\).

  • What is the significance of the vector product's magnitude?

    It equals the area of the parallelogram spanned by the two vectors.

  • When is the vector product zero?

    When the two vectors are parallel or anti-parallel (angle 0° or 180°).

  • What are the properties of the vector product?

    It is anticommutative: 𝑎⃗ × 𝑏⃗ = - 𝑏⃗ × 𝑎⃗, and distributes over addition.