Question

2 vectors of magnitude 9&7inclined at 60° calculate magnitude of resultant ?what angle is the resultant incline to vector of magnitude 9?

Answer 1

P = 9      Q = 7        Ф = 60°

Resultant R is given by parallelogram law of forces
magnitude R² = P² + Q² + 2 PQ cos Ф = 81 + 49 + 2 7 * 9 cos 60°
         R = √193  units

Angle made by R with P = 9  is given by
    tan α = P sin Ф / [ P + Q cos Ф]  = 9 sin 60° / [ 9 + 7 cos 60° ]
           = 0.623

         α = 31.945°  angle made by Resultant with vector of magnitude 9