Q. Let aˉ=i^+2j^−k^ and bˉ=i^+j^−k^ be two vectors. If cˉ is a vector such that bˉ×cˉ=bˉ×aˉ and cˉ⋅aˉ=0, then cˉ⋅bˉ is
Identify Cross Product Equation: Identify the cross product equation. bˉ×cˉ=bˉ×aˉ
Calculate Cross Product: Calculate the cross product bˉ×aˉ.bˉ×aˉ=(i^+j^−k^)×(i^+2j^−k^)bˉ×aˉ=i^×i^+i^×2j^+i^×(−k^)+j^×i^+j^×2j^+j^×(−k^)−k^×i^−k^×2j^−k^×(−k^)bˉ×aˉ=0+2k^−j^−j^+0+i^+i^−2k^+0bˉ×aˉ=2i^−2j^
Find Cross Product Equality: Since bˉ×cˉ=bˉ×aˉ, we have bˉ×cˉ=2i^−2j^.
Identify Dot Product Equation: Identify the dot product equation. cˉ⋅aˉ=0
Use Dot Product Equation: Use the dot product equation to find components of cˉ. Let cˉ=xi^+yj^+zk^. cˉ⋅aˉ=(xi^+yj^+zk^)⋅(i^+2j^−k^)cˉ⋅aˉ=x⋅1+y⋅2+z⋅(−1)cˉ⋅aˉ=x+2y−z Since cˉ⋅aˉ=0, we have x+2y−z=0.
Calculate Dot Product of c and b: Now, calculate cˉ⋅bˉ using the components of cˉ.cˉ⋅bˉ=(xi^+yj^+zk^)⋅(i^+j^−k^)cˉ⋅bˉ=x⋅1+y⋅1+z⋅(−1)cˉ⋅bˉ=x+y−z
Calculate Dot Product of c and b: Now, calculate cˉ⋅bˉ using the components of cˉ.cˉ⋅bˉ=(xi^+yj^+zk^)⋅(i^+j^−k^)cˉ⋅bˉ=x⋅1+y⋅1+z⋅(−1)cˉ⋅bˉ=x+y−zWe know bˉ×cˉ=2i^−2j^, which means the i and j components of cˉ must be such that when crossed with b1, they give b2. However, we made a mistake in the cross product calculation earlier. Let's correct it.
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