Two forces of equal magnitude F act at an angle of 120 degrees to each other. Their resultant has magnitude
Correct answer: C. F
- A. 2F
- B. F times the square root of 3
- C. F
- D. zero
Explanation
Using the parallelogram rule, the resultant is the square root of (F squared plus F squared plus 2F squared cos 120), and since cos 120 is minus one half the last term cancels one of the others, leaving the square root of F squared, which is F. Equal vectors at 120 degrees are the arrangement in which three such vectors would sum to zero. At 0 degrees the resultant would be 2F and at 180 degrees it would be zero.
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About Addition of Vectors
Vector addition combines directed quantities using the head-to-tail, parallelogram and component methods. Work includes finding the resultant magnitude and direction for two or more vectors, resolving vectors into perpendicular components, and distinguishing vector addition from scalar addition, where direction has no role.
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