Question 13 (1 point) Forces of 2.4 N and 1.8 N act on an object in opposite directions to one another. What is the magnitude of a third force acting on the same object so that it remains stationary? Question 14 (1 point) Lars puts on a pair of wooden skis, and stands erect on a level snowfield. The coefficient of static friction between his skis and the snow is 0.22. If he has a mass of 75 kg, what is the minimum force required to start him moving across the snow? Question 15 (1 point) How does a sprinter accelerate? O by using the normal force between her body and the ground 0 by using the kinetic friction between her shoes and the ground 0 by using the static friction between her shoes and the ground 0 by using the force of gravity