Three vectors A, B, and C add up to zero. Then:
1. | vector (A×B)×C is not zero unless vectors B and C are parallel. |
2. | vector (A×B).C is not zero unless vectors B and C are parallel. |
3. | if vectors A, B and C define a plane, (A×B)×C is in that plane. |
4. | (A×B).C = |A||B||C| → C2 = A2 + B2 |
The incorrect statement/s is/are:
1. (b, d)
2. (a, c)
3. (b, c, d)
4. (a, b)
(1) Hint: The resultant of three vectors will be equal to zero only if the vectors are coplanar.
Step 1: Find if the vectors are coplanar.
Given, A + B + C = 0
Hence, we can say that A, B, and C are in one plane and are represented by the three sides of a triangle taken in one order.
Step 2: Find the incorrect statements one by one.
It cannot be zero as
If B and C are not parallel, then (AxB) will be perpendicular to the plane of A, B and C.
Hence, (AxB).C = 0 whatever be the situation is. Hence, statement (b) is incorrect and option.
Also, (AxB)xC will be in the plane of A, B and C and statement (c) is correct.
Statement (d) is also incorrect as discussed already.
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