# A box of books weighing 325 N moves at a constant velocity across the floor when the box is pushed with a force of 425 N exerted downward at an angle of 35.2 degrees below the horizontal. Fink Mu,k between the box and the floor.

There have been several of this type of question posted here today. Take a look at how they were done.

Each can be solved by writing down Newton's second law. The force "F" in the law F= m a is the net force. In this case, the acceleration a is zero. Therefore the applied force component along the direction of motion equals the friction force. Write that statement in algebraic form and solve for Mu,k.