posted by poop .
a college student takes her book to class by placing them in a box and pulling it around school. She pulls on the box with a force of 90N at a angle of 30 relative to the horizontal. the box of books has a mass of 20 kg and the coefficiant of kinetic friction between the bottom of the box and the sidwalk is 0.5. What is the net froce acting horizontally and what is the acceleration of the box.