In order to find the force (F), you would have to use the formula for it: F=ma where m is mass and a is acceleration. In the problem, the mass is 2.85kg and the acceleration is 4.9m/s^2. Therefore, F=2.85kg(4.9m/s^2) F=13.965kg(m/s^2) Since N=kg(m/s^2) F=13.965N And because the problem requires that we use only 2 significant figures, F=13N Therefore, the student must exert 13N of force.