Chapter 10, Problem 54P

In a judo foot-sweep move, you sweep your opponent's left foot out from under him while pulling on his gi (uniform) toward that side. As a result, your opponent rotates around his right foot and onto the mat. Figure 10-44 shows a simplified diagram of your opponent as you face him, with his left foot swept out. The rotational axis is through point O. The gravitational force $\stackrel{\to }{F_g}$ on him effectively acts at his center of mass, which is a horizontal distance d = 28 cm from point O. His mass is 70 kg, and his rotational inertia about point O is 65 kg · m². What is the magnitude of his initial angular acceleration about point O if your pull $\stackrel{\to }{F_a}$ on his gi is (a) negligible and (b) horizontal with a magnitude of 300 N and applied at height h = l.4m?

Figure 10-44 Problem 54.