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ConcepTest 6 Followup. 0 = -0.5*9.8t 2 + V oy t, 4.9t 2 - V 0 sin( q )t = 0. t{4.9t - V 0 sin( q )}= 0. Thus, t = 0 or t = V 0 sin( q )/4.9. Which cannon ball hits the ground first?. Cannon Ball A Cannon Ball B Both cannon balls hit the ground at the same time. B. A. Marker. y.
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ConcepTest 6 Followup • 0 = -0.5*9.8t2 + Voyt, • 4.9t2 - V0sin(q)t = 0. • t{4.9t - V0sin(q)}= 0. Thus, t = 0 or t = V0sin(q)/4.9 Which cannon ball hits the ground first? Cannon Ball A Cannon Ball B Both cannon balls hit the ground at the same time. B A Marker
y Example Problem #3.21 v0x = v0cos600 = 3.2 m/s v0y = v0sin600 = 5.54 m/s v0 = 6.4 m/s y = ? 600 x x = 2.1 m • (a) Basically means, “Find value of y when x = 2.1 m.” • Find time when x = 2.1 m: x = 2.1 m = x0 + v0xt = 0 + v0xt t = 2.1 m / 3.2 m/s t = 0.656 s • Now substitute this into equation for y: y = y0 + voyt – 0.5gt2 y = 0 + (5.54 m/s)(0.656 s) – 0.5(9.8 m/s2)(0.656 s)2 = 1.53 m (b) vy = v0y – gt = 5.54 m/s – (9.8 m/s2)(0.656 s) = –0.89 m/s
N F = 80 N W Example Problem #4.10 Free-body diagram: y x (a) S Fx = max S Fy = may = 0 (no motion in y – direction) F = max N – W = 0 N = W All acceleration is in the x – direction , so use atotal = ax = 2(x – x0) / t2.