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Physics Question
發問:
Show the steps clearly and briefly explain.1. A man near the edge of a cliff projects a stone vertically upwards. The height of the cliff is 56m above sea level and the stone reaches the sea after 4s. Assume the air resistance is negligible.(a) Find the initial speed of the stone.(b) How high does it reach... 顯示更多 Show the steps clearly and briefly explain. 1. A man near the edge of a cliff projects a stone vertically upwards. The height of the cliff is 56m above sea level and the stone reaches the sea after 4s. Assume the air resistance is negligible. (a) Find the initial speed of the stone. (b) How high does it reach above its starting point? (c) How long does it take for the stone to reach the highest point? (d) Sketch the velocity-time graph for the motion. (Take upward direction as positive) 更新: (e) Sketch the acceleration time-graph for the motion. (Take upward direction as positive) 更新 2: Why s = -56 m? <------ Why it is a -ve number?
最佳解答:
(a) Taking upward direction as positive, we have: Initial velocity = +u m/s Applying the equation s = ut + (1/2)at2 with s = -56 m, a = -10 m/s-2 and t = 4: -56 = 4u - 5 × 42 4u = 80 - 56 u = 6 m/s (b) Applying the equation v2 - u2 = 2as with a = -10 m/s-2, u = 6 m/s and v = 0 m/s: 0 - 62 = 2 (-10) s s = 1.8 m So the stone reaches a height of 1.8 m above its starting point. (c) Applying the equation v= u + at with a = -10 m/s-2, u = 6 m/s and v = 0 m/s: 0 = 6 - 10t t = 0.6 s So it taks 0.6 s for the stone to reach the highest point. (d) Sketch of v-t graph: 圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Oct07/Crazymech6.jpg (d) Sketch of a-t graph: 圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Oct07/Crazymech7.jpg
其他解答:
Physics Question
發問:
Show the steps clearly and briefly explain.1. A man near the edge of a cliff projects a stone vertically upwards. The height of the cliff is 56m above sea level and the stone reaches the sea after 4s. Assume the air resistance is negligible.(a) Find the initial speed of the stone.(b) How high does it reach... 顯示更多 Show the steps clearly and briefly explain. 1. A man near the edge of a cliff projects a stone vertically upwards. The height of the cliff is 56m above sea level and the stone reaches the sea after 4s. Assume the air resistance is negligible. (a) Find the initial speed of the stone. (b) How high does it reach above its starting point? (c) How long does it take for the stone to reach the highest point? (d) Sketch the velocity-time graph for the motion. (Take upward direction as positive) 更新: (e) Sketch the acceleration time-graph for the motion. (Take upward direction as positive) 更新 2: Why s = -56 m? <------ Why it is a -ve number?
最佳解答:
(a) Taking upward direction as positive, we have: Initial velocity = +u m/s Applying the equation s = ut + (1/2)at2 with s = -56 m, a = -10 m/s-2 and t = 4: -56 = 4u - 5 × 42 4u = 80 - 56 u = 6 m/s (b) Applying the equation v2 - u2 = 2as with a = -10 m/s-2, u = 6 m/s and v = 0 m/s: 0 - 62 = 2 (-10) s s = 1.8 m So the stone reaches a height of 1.8 m above its starting point. (c) Applying the equation v= u + at with a = -10 m/s-2, u = 6 m/s and v = 0 m/s: 0 = 6 - 10t t = 0.6 s So it taks 0.6 s for the stone to reach the highest point. (d) Sketch of v-t graph: 圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Oct07/Crazymech6.jpg (d) Sketch of a-t graph: 圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Oct07/Crazymech7.jpg
其他解答:
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