Question Detail

PHY 101 PHY 101 Past Questions Objective Question
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Question

Given that A = 4i + 2k, B = -3i - 3k and C = 6i - 4k. Find A · (B × C).
Options
A 7i - 5k
B -72i + 24k
C 0
Correct Answer
D 7i + 5k
Correct Answer

Option C is the correct answer.

Detailed Explanation

First compute B × C. B = -3i + 0j - 3k, C = 6i + 0j - 4k. B × C = determinant |i j k; -3 0 -3; 6 0 -4| = i(0×(-4) - (-3)×0) - j((-3)×(-4) - (-3)×6) + k((-3)×0 - 0×6) = i(0 - 0) - j(12 + 18) + k(0) = -30j. Then A · (B × C) = (4i + 0j + 2k) · (-30j) = 0. So scalar triple product is 0.

Hint

Scalar triple product can be zero if vectors are coplanar.

Question Info

Course: PHY 101
Topic: PHY 101 Past Questions
Type: Objective
Difficulty: Not specified
Question 1046 of 1250
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