A student pulls a box of books on a smooth horizontal oor with a force of 100 N in a direction of 45 above the horizontal. If the mass of the box and the books is 40.0 kg, what is the acceleration of the box? 0 2.0 m/s2 0 1.5 m/s2 0 1.25 m/s2 0 3.3 m/s2