During knee extension the patella moves in the groove between the medial and lateral condyles of the femur. An imbalance between the four muscles that pull on the patella can result in the patella’s not tracking correctly. This can occur, for example, if the knee has been immobilized in a cast for a period of time and the vastus medials and lateralis muscles have not atrophied at the same rate. Given the following magnitudes and direction for the four muscle force vectors, determine the resultant vector:

Rectus femoris 130N, 0.25 rad to the left of vertical

Vastus lateralis 180N, 0.50 rad to the left of vertical

Vastus intermedius 165N, 0.15 rad to the left of vertical

Vastus medialis 210N, 0.62 rad to the right of vertical