This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
When two forces or more act on one object, the net force or the resultant force is found by using the parallelo gram law of forces or vectors. If P & Q are forces, construct a parallelogram with the sides proportional to their magnitudes, and the angle between them equal to the angle Ф betwen the forces.

Then the resultant of the two forces is the diagonal passing the intersection of the two forces.
so the length of the diagonal = resultant force = R
R² = P² + Q² + 2 P Q cos Ф
the angle made by R with P is given by :  tan α  =  Q sin Ф / (P+Q cosФ)

R = 20√3 Newton          Ф = 60 deg         cos Ф= 1/2
forces are equal P = Q
So (20√3)² = P² + P² + 2 P P 1/2    
=>  400 * 3 =  3 P²  => P² = 400    So  P = 20  newotns