A boy throws a ball upward from the top of a cliff with a speed of 14.7m/s on the way down it just misses the thrower and fall the ground 49m below .find how long the ball rises?how high it goes ?how long it is in air and ?with what velocity it strikes the ground?
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Explanation:
v = u - gt = 14.7 - 9.8t , t = 147/98 = 1.5 s
h = height above cliff top , 2gh = u² , h = u²/2g = 14.7²/19.6 = 11.025 m.
y = ut - 1/2 gt² , - 49 = 14.7t - 4.9t² , t² - 0.3t - 10 =0
t = 0.3 ± √40.09 ÷ 2 = 3.32 s
v² = u² - 2gy = 14.7² + 2x9.8x49 = 49²( 0.49) , v = 4.9 m/s
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