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Unformatted text preview: 1 Chap. 11, HW1 Questions 3. Figure 1124 shows two particles A and B at xyz coordinates (1 m, 1 m, 0) and (1 m, 0, 1 m). Acting on each particle are three numbered forces, all of the same magnitude and each directed parallel to an axis. (a) Which of the forces produce a torque about the origin that is directed parallel to y ? force 5, 6 (use F r = ) (b) Rank the forces according to the magnitudes of the torques they produce on the particles about the origin, greatest first. Rank: 1 and 4 tie, 2, 3, 5, 6 all tie Problems 3. A 140 kg hoop rolls along a horizontal floor so that the hoop's center of mass has a speed of 0.150 m/s. How much work must be done on the hoop to stop it? ( ) ( ) ( ) ( ) J 15 . 3 Here 2 2 2 1 2 2 2 1 2 2 2 1 2 2 1 = = + = = = + + = + = + mv mv R v mR W mR I W mv I W K K W U K i f 4. A uniform solid sphere rolls down an incline. (a) What must be the incline angle if the linear acceleration of the center of the sphere is to have a magnitude of 0.10 g ? A free body diagram is shown below. 2 . 8 10 5 7 sin 10 Using 5 7 sin g 5 2 sin g equation first the using equation second in the for ng Substituti sin : ) (along al Tranlation 5 2 : center about Torque = = = = = = = = . g . a a Ma Ma M f Ma f F x R a MR R f I s s g s v 2 (b) If a frictionless block were to slide down the incline at that angle, would its...
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 Spring '08
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