Vectors

  • Vectors are quantities that have both magnitude and direction.
  • They are often represented by an arrow where the length of the arrow represents the magnitude and the direction of the arrow represents the direction of the vector.
  • Vectors can be added, subtracted, and multiplied by scalars.
  • Scalar multiplication involves multiplying the magnitude of the vector by a scalar.
  • Vectors can also be multiplied using the dot product and cross product. Examples:
  • Displacement of an object
  • Force exerted on an object
  • Velocity of an object Equations:
  • Magnitude of a vector: |π‘Žβƒ— | = √(π‘Žπ‘₯Β² + π‘Žπ‘¦Β²)
  • Unit vector: 𝑒⃗ = π‘Žβƒ— / |π‘Žβƒ— |
  1. Vector Addition
  • Vectors can be added together using the parallelogram law.
  • To add two vectors, place the tail of the second vector at the head of the first vector.
  • The sum of the two vectors is the vector that extends from the tail of the first vector to the head of the second vector.
  • The order in which the vectors are added does not matter; the result will be the same.
  • Vector addition is both commutative and associative. Example:
  • A vector π‘Žβƒ— = 3𝑖̂ + 2𝑗̂ and 𝑏⃗ = -𝑖̂ + 4𝑗̂. Find the sum 𝑐⃗ = π‘Žβƒ— + 𝑏⃗. Equation:
  • 𝑐⃗ = π‘Žβƒ— + 𝑏⃗ = (3𝑖̂ + 2𝑗̂) + (-𝑖̂ + 4𝑗̂)
  1. Vector Subtraction
  • Vector subtraction is similar to vector addition, but in the opposite direction.
  • To subtract two vectors, we add the negative of the second vector to the first vector.
  • The result is a vector that points from the tail of the second vector to the head of the first vector. Example:
  • A vector π‘Žβƒ— = 3𝑖̂ + 2𝑗̂ and 𝑏⃗ = -𝑖̂ + 4𝑗̂. Find the difference 𝑑⃗ = π‘Žβƒ— - 𝑏⃗. Equation:
  • 𝑑⃗ = π‘Žβƒ— - 𝑏⃗ = (3𝑖̂ + 2𝑗̂) - (-𝑖̂ + 4𝑗̂)
  1. Scalar Multiplication
  • Scalar multiplication involves multiplying a vector by a scalar (a real number).
  • To multiply a vector by a scalar, multiply each component of the vector by the scalar.
  • The direction of the resulting vector remains the same, but the magnitude is scaled by the scalar. Example:
  • Multiply the vector π‘Žβƒ— = 2𝑖̂ + 3𝑗̂ by the scalar 5. Equation:
  • 𝑏⃗ = 5(2𝑖̂ + 3𝑗̂)
  1. Dot Product
  • The dot product, also known as the scalar product, is a binary operation that takes two vectors and produces a scalar.
  • The dot product of two vectors π‘Žβƒ— and 𝑏⃗ is denoted as π‘Žβƒ— Β· 𝑏⃗.
  • The dot product is computed by multiplying the corresponding components of the vectors and summing the products.
  • The dot product is commutative: π‘Žβƒ— Β· 𝑏⃗ = 𝑏⃗ Β· π‘Žβƒ—.
  • Geometrically, the dot product can be interpreted as the product of the magnitudes of the two vectors and the cosine of the angle between them. Example:
  • Calculate the dot product of π‘Žβƒ— = 2𝑖̂ + 3𝑗̂ and 𝑏⃗ = -𝑖̂ + 4𝑗̂. Equation:
  • π‘Žβƒ— Β· 𝑏⃗ = (2𝑖̂ + 3𝑗̂) Β· (-𝑖̂ + 4𝑗̂)
  1. Properties of the Dot Product
  • Distributive Property: π‘Žβƒ— Β· (𝑏⃗ + 𝑐⃗) = π‘Žβƒ— Β· 𝑏⃗ + π‘Žβƒ— Β· 𝑐⃗
  • Scalar Multiplication: (π‘Žπ‘βƒ—) Β· 𝑐⃗ = π‘Žβƒ— Β· (𝑏𝑐⃗) = π‘Žπ‘π‘βƒ— Β·
  • Dot Product with the Zero Vector: π‘Žβƒ— Β· 𝑣⃗ = 0 Example:
  • Verify the distributive property: (π‘Žβƒ— Β· 𝑏⃗)βƒ— + (π‘Žβƒ— Β· 𝑐⃗)βƒ— = π‘Žβƒ— Β· (𝑏⃗ + 𝑐⃗)βƒ—. Equation:
  • (π‘Žβƒ— Β· 𝑏⃗)βƒ— + (π‘Žβƒ— Β· 𝑐⃗)βƒ— = π‘Žβƒ— Β· (𝑏⃗ + 𝑐⃗)βƒ— = ?
  1. Cross Product
  • The cross product, also known as the vector product, is a binary operation that takes two vectors and produces another vector.
  • The cross product of two vectors π‘Žβƒ— and 𝑏⃗ is denoted as π‘Žβƒ— Γ— 𝑏⃗.
  • The cross product is computed using the determinant of a 3x3 matrix involving the components of the vectors.
  • The resulting vector is orthogonal to both the original vectors and its direction is determined by the right-hand rule. Example:
  • Calculate the cross product of π‘Žβƒ— = 2𝑖̂ + 3𝑗̂ + π‘˜Μ‚ and 𝑏⃗ = -𝑖̂ + 4𝑗̂ - 2π‘˜Μ‚. Equation:
  • π‘Žβƒ— Γ— 𝑏⃗ = (2𝑖̂ + 3𝑗̂ + π‘˜Μ‚) Γ— (-𝑖̂ + 4𝑗̂ - 2π‘˜Μ‚)
  1. Properties of the Cross Product
  • The cross product is distributive: π‘Žβƒ— Γ— (𝑏⃗ + 𝑐⃗) = π‘Žβƒ— Γ— 𝑏⃗ + π‘Žβƒ— Γ— 𝑐⃗
  • Scalar Multiplication: π‘Žβƒ— Γ— (𝑏𝑐⃗) = (π‘Žβƒ— Γ— 𝑏⃗)𝑐⃗ = π‘Žπ‘βƒ— Γ— 𝑐⃗
  • The cross product of two parallel vectors is the zero vector: π‘Žβƒ— Γ— 𝑏⃗ = 𝑣⃗ Example:
  • Verify the distributive property: π‘Žβƒ— Γ— (𝑏⃗ + 𝑐⃗) = π‘Žβƒ— Γ— 𝑏⃗ + π‘Žβƒ— Γ— 𝑐⃗. Equation:
  • π‘Žβƒ— Γ— (𝑏⃗ + 𝑐⃗) = π‘Žβƒ— Γ— 𝑏⃗ + π‘Žβƒ— Γ— 𝑐⃗ = ?
  1. Applications of Vectors: Displacement
  • Vectors are commonly used to represent the displacement of an object.
  • Displacement is a vector quantity that represents the change in position of an object from its initial position to its final position.
  • Displacement is defined as the vector that points from the initial position to the final position of the object.
  • Displacement can be measured in terms of magnitude and direction or using components in a coordinate system. Example:
  • An object moves 5 meters east and then 3 meters north. What is the displacement of the object? Equation:
  • π‘Žβƒ— = 5𝑖̂ + 3𝑗̂
  1. Applications of Vectors: Force
  • Vectors are used to represent forces acting on an object.
  • Force is a vector quantity that represents the physical interaction between two objects.
  • A force is characterized by its magnitude and direction.
  • Forces can be added and subtracted using vector addition and subtraction. Example:
  • Two forces, 𝐹⃗1 = 5𝑖̂ - 2𝑗̂ and 𝐹⃗2 = -3𝑖̂ + 𝑗̂, act on an object. What is the resulting force? Equation:
  • 𝐹⃗ = 𝐹⃗1 + 𝐹⃗2
  1. Applications of Vectors: Velocity
  • Vectors are commonly used to represent the velocity of an object.
  • Velocity is a vector quantity that represents the rate of change of displacement with respect to time.
  • Velocity is defined as the vector that points in the direction of motion and has a magnitude equal to the speed of the object.
  • Velocity can be measured in terms of magnitude and direction or using components in a coordinate system. Example:
  • An object moves 10 meters east in 2 seconds. What is the velocity of the object? Equation:
  • 𝑣⃗ = 𝑑⃗ / 𝑑