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Condition where objects are moving through space neglecting air resistance Vertically, the only thing acting on the object is gravity Acceleration due to gravity: ◦ ag = 9.8 m/s2 A pebble is dropped into a deep well, and the sound of the splash is heard 3 s later. How deep is the well? (Ignore the time for the sound to reach your ears) v0 = 0 m/s ag = 9.8 m/s t=3s Given: ◦ v0 = 0 m/s ◦ t = 3s ◦ a = 9.8 m/s2 Equation: d = do + vot + ½ at2 Trying to find: ◦ d=? Solve: d = 0 +(0)(3) + ½ (9.8)(32) d = 44.1 m A ball is thrown vertically upward with a speed of 25 m/s. – How high does it – How long does it – How long does it – What is its speed vf = 0 m/s ag = -9.8 m/s v0 = 25 m/s rise? take to reach its highest point? take to reach the ground again? when it returns to the ground? v0 = 0 m/s ag = 9.8 m/s Given: ◦ v0 = 25 m/s ◦ vf = 0 m/s ◦ a = -9.8 m/s2 Trying to find: ◦d=? ◦t=? Equation: vf2 = vo2 + 2ad Solve: (0)2 = (25)2 + 2(-9.8)(d) d =31.9 m Equation: vf = vo + at Solve: 0 = 25 + (-9.8)(t) t = 2.55 s Given: ◦ v0 = 0 m/s ◦ d = 31.9 ◦ a = 9.8 m/s2 Trying to find: ◦ vf = ? ◦t=? Equation: vf2 = vo2 + 2ad Solve: (vf)2 = (0)2 + 2(9.8)(31.9) vf = 25 m/s Equation: vf = vo + at Solve: 25 = 0 + (9.8)(t) t = 2.55 s Time up = Time Down •The distance up is the same as the distance down •the acceleration is the same, just moving in an opposite direction •Therefore is must be the same time! Velocity up = Velocity Down •The distance up is the same as the distance down •the acceleration is the same, just moving in an opposite direction •the time is the same •Therefore it must be the same velocity! Chapter 5 #67, 70, 71, 74, 76 Due Wednesday