if the resultant of two forces of magnitudes P and Q acting at a point at an angle of 60° is √7Q, then P/Q is
(a)1 (b)3/2 (c)2 (d)4
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Answered by
67
Answer:
P/Q = -3 or 2
Step-by-step explanation:
if the resultant of two forces of magnitudes P and Q acting at a point at an angle of 60° is √7Q, then P/Q is
(a)1 (b)3/2 (c)2 (d)4
Resulatnt = √P² + Q² + 2PQCos60
√P² + Q² + 2PQCos60 = √7Q
Squaring both sides
P² + Q² + PQ = 7Q²
Let say P/Q = k => P = kQ
=> k²Q² + Q² + kQ² = 7Q²
=> k² + 1 + k = 7
=> k² + k - 6 = 0
=> k² + 3k -2k - 6 = 0
=> (k + 3)(k - 2) = 0
=> k = -3 or 2
=> P/Q = -3 or 2
Answered by
7
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