84. 4 relative velocity addition and accelerations From the problem we can know that TThat means in G=l(4cos 6+3ti +4 sin 6t j x=-4cos63=0 3km/h 4km0.75 6=41° ybG=4 sin 8t=0 0.15 =0.06h≈3min 4sin41 84.5 The circular motion 1. Uniform circular motion A circular motion at constant speed The motion of a particle a bout a point Experiment: the direction of the acceleration We can demonstrate that the magnitude of centripetal acceleration is r:4e 1313 From the problem we can know that = 0 bG x That means 0.06h 3min. 4sin41 0.15 4 sin 0.15km 41 0.75 4km/h 3km/h cos 4cos 3 0 ˆ 4 sin ˆ in [( 4cos 3] = = ≈ = = = = = = − + = = − + + o o r t y t x r ti t j bG bG bG θ θ θ θ θ θ §4.4 relative velocity addition and accelerations §4.5 The circular motion 1. Uniform circular motion v r v r ∆θ r r A circular motion at constant speed The motion of a particle about a point We can demonstrate that the magnitude of centripetal acceleration is r v ac 2 = Experiment: the direction of the acceleration