JEE Main2002MathematicsVector AlgebraActual

The sum of two forces is 18 N and resultant whose direction is at right angles to the smaller force is 12 N. The magnitude of the two forces are

Options

A13, 5
B12, 6
C14, 4
D11, 7

Correct answer

A. 13, 5

Step-by-step solution

Let two forces be P and Q . Given P+Q=18 and P a +Q b =12 c P a -12 c = Q b aligned & P^2+144=Q^2=(18-P)^2 ; P^2+144=324-36 P+P^2 & 36 P=180 P=5 and Q=13 aligned (where a and b are unit vectors along P and Q ).

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