Question Detail

PHY 101 PHY 101 Past Questions Objective Question
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Question

If A = 2i + 4j - 5k, the direction of cosines of the vector along the z-axis is
Options
A 2/√45
B 4/√45
C -5/√45
Correct Answer
D √45
Correct Answer

Option C is the correct answer.

Detailed Explanation

Direction cosines are the cosines of the angles the vector makes with the coordinate axes. For the z-axis, the direction cosine is the k-component divided by the magnitude. Magnitude |A| = √(2² + 4² + (-5)²) = √(4 + 16 + 25) = √45. So direction cosine along z = -5/√45.

Hint

Direction cosine for a component = component/magnitude.

Question Info

Course: PHY 101
Topic: PHY 101 Past Questions
Type: Objective
Difficulty: Not specified
Question 863 of 1250
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