In a two-dimensional tug-of-war, Alex, Betty, and Charles pull horizontally on an automobile tire at the angles shown in the overhead view of Fig. 5-33. The tire remains stationary in spite of the three pulls. Alex pulls withe force Fa of magnitude 220N and Charles pulls with force Fc of magnitude 170N. Note that the direction of Fc is not given. What is the magnitude of Betty's force Fb?

Answer 1

The "angles shown in the overhead view" are needed to answer your question. You have not provided them.

Vector Fc is the equilbrant (negative resultant) of Fa and Fb