If A = 3i - 2j and B = -i + 4j, what is the scalar product A · B?

Practice Questions

Q1
If A = 3i - 2j and B = -i + 4j, what is the scalar product A · B?
  1. -11
  2. -5
  3. -7
  4. -9

Questions & Step-by-Step Solutions

If A = 3i - 2j and B = -i + 4j, what is the scalar product A · B?
  • Step 1: Identify the components of vector A. A = 3i - 2j means A has a component of 3 in the i direction and -2 in the j direction.
  • Step 2: Identify the components of vector B. B = -i + 4j means B has a component of -1 in the i direction and 4 in the j direction.
  • Step 3: Write down the formula for the scalar product (dot product) of two vectors A and B. The formula is A · B = (A_i * B_i) + (A_j * B_j), where A_i and A_j are the components of A, and B_i and B_j are the components of B.
  • Step 4: Substitute the components of A and B into the formula. A · B = (3 * -1) + (-2 * 4).
  • Step 5: Calculate the first part of the equation: 3 * -1 = -3.
  • Step 6: Calculate the second part of the equation: -2 * 4 = -8.
  • Step 7: Add the results from Step 5 and Step 6: -3 + (-8) = -3 - 8.
  • Step 8: Simplify the final result: -3 - 8 = -11.
  • Vector Operations – Understanding how to perform operations on vectors, specifically the scalar (dot) product.
  • Component-wise Multiplication – Knowing how to multiply corresponding components of vectors and sum the results.
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