A vector perpendicular to both A⃗=î+2ĵ+2k̂ and B⃗=2î-ĵ+2k̂ has magnitude 9. Which pair gives the two possible vectors?
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Question

A vector perpendicular to both A⃗=î+2ĵ+2k̂ and B⃗=2î-ĵ+2k̂ has magnitude 9. Which pair gives the two possible vectors?

G1 Physics · Accepted Answer

A×B=(6,2,−5), whose magnitude is √65, not 9. A magnitude-9 perpendicular vector is ±(9/√65)(6î+2j−5k̂).