Three students converge on the last textbook in the store. All three grab it and begin to pull in the directions shown in the above figure. Student A exerts a force of 77.64 N, student B pulls with a force of 18.52 N, and student C pulls with a force of 66.43 N at an angle θ(theta)=70.49 degrees above the -x axis.

Question

Three students converge on the last textbook in the store. All three grab it and begin to pull in the directions shown in the above figure. Student A exerts a force of 77.64 N, student B pulls with a force of 18.52 N, and student C pulls with a force of 66.43 N at an angle θ(theta)=70.49 degrees above the -x axis. 
Considering these three forces (ignore the force of gravity on the book), what is the magnitude of the net force on the book?

Steve · Answer

resolve the three forces into x- and y-components. Add them up, and take the magnitude.