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3-3 (j) Parallel vectors

3-3 (j) Parallel vectors

Point 4 of 7 — The Vector (Cross) Product and the Scalar Triple ProductQuestion bank: 0 questions (0 with pictures)

04 3-3 (j) Parallel vectors

Condition

  • Two non-zero vectors are parallel if and only if A⃗×B⃗=0⃗, that is AxBx=AyBy=AzBz=k
  • Equivalent form: A⃗=kB⃗. If k>0 they have the same direction; if k<0 they are opposite.
  • If a component of B⃗ is zero, the matching component of A⃗ must also be zero.
✍️ Worked examples

Example 7: Find m and k if A⃗=(2,−3,m) is parallel to B⃗=(1,k,8).

Solution:

  • 21=−3k=m8.
  • −3k=2 gives k=−32.
  • m8=2 gives m=16.
  • The vectors are in the same direction since the ratio 2 is positive.

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