The drawing shows a bike wheel resting against a small step whose height is h=0.120m. The weight and radius of the wheel are W = 25.0N and r = 0.340m. A horizontal force F is applied ot eh axle of the weehl. As the magnitude of F increases, there comes a time when the wheel just begins to rise up and loses contact with the ground. What is the magnitude of the force when this happens? I do not even know where to start. I tried to think of torques, but Fg acts on the center of the wheel, whose distance is 0 from the radius. I also tried to think of a normal force exerted by the step, but that just got really weird. Finally, I thought about friction from the floor below the step, but it didin't work out as well. And the other problem was the force exerted by the horizontal force, which is also 0 from the radius since it acts directly on the axle. And as an extention, can I prove that the height of the step must be between 0 and the radius of the wheel?