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標題:
a flea jump up
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a) If a flea can jump straight up to a height of 0.440m, what is its initial speed as it leaves the ground? b) How long is it in the air? ans: a) 2.94m/s b) 0.6s
最佳解答:
(a) Use equation of motion: v^2 = u^2 + 2a.s with v = 0 m/s, a = -g(= -9.81 m/s^2), s = 0.44 m, u =? hence, 0 = u^2 + 2.(-9.81).(0.44) u = 2.94 m/s The initial jumping speed of the flea is 2.94 m/s. (b) Use equation of motion: s = ut + (1/2)at^2 with s = 0 m, u = 2.94 m/s, a = -g(=-9.81 m/s^2), t=? Hence, 0 = 2.94t + (1/2).(-9.81)t^2 t = 2.94 x 2/9.81 s = 0.6 s The time for the flea in air is 0.6 s
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