Question 48 of 68intermediate🔧 ApplyMCQ1 mark

Let the vectors a⃗ and b⃗ be such that |a⃗| = 3 and |b⃗| = 2\sqrt{2}/3, then a⃗ × b⃗ is a unit vector, if the angle between a⃗ and b⃗ is

Exercise: EXERCISE 10.4 | Q: 11 | (Page 32)
For More Understanding

Explanation

For the cross product vector a⃗ × b⃗ to be a unit vector, its magnitude must equal 1. The magnitude of a cross product is given by |a⃗ × b⃗| = |a⃗| |b⃗| sin θ, where θ is the angle between the two vectors. Given |a⃗| = 3 and |b⃗| = 2\sqrt{2}/3, we set up the equation: 3 × (2\sqrt{2}/3) × sin θ = 1, which simplifies to 2\sqrt{2} × sin θ = 1, giving sin θ = 1/2\sqrt{2}. Since sin(π/4) = 1/2\sqrt{2}, the angle between the vectors must be π/4.

Solution Steps

  1. Step 1: For a⃗ × b⃗ to be a unit vector, |a⃗ × b⃗| = 1

  2. Step 2: Using the formula |a⃗ × b⃗| = |a⃗| |b⃗| sin θ

  3. Step 3: Substitute given values: 3 × (2\sqrt{2}/3) × sin θ = 1

  4. Step 4: Simplify: 2\sqrt{2} × sin θ = 1

  5. Step 5: Solve: sin θ = 1/2\sqrt{2}

  6. Step 6: Therefore, θ = π/4 (since sin π/4 = 1/2\sqrt{2})