What will be the magnitude of the resultant velocity?

Two velocities of magnitudes 10 m/s and 20 m/s are moving in a direction so that the angle between these two velocities is 60°. What will be the magnitude of the resultant velocity?

a. 26.45
b. 25.45
c. 27.37
d. 30.33

Correct Answer : a. 26.45

Explanation :

According to the law of parallelogram of velocities, if two velocities are presented in magnitude and direction by two adjacent sides of a parallelogram, their resultant will be represented in magnitude and direction by the diagonal of the parallelogram. So using this equation w² =u² + v² + 2uv cos(a). Where w, u and v are the magnitudes of the resultant, first and second velocities respectively.