# physics

i dont know what the answer is... i got itwrong my answer was 1.78. whats the correct answer?

A 57kg trampoline artist jumps vertically upward from the top of a platform with a speed of 4.7m/s. How fast is he going as he lands on the trampoline 3.8m below?

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1. his final KE=KE at launch + PE at launch
1/2 mv^2=1/2 m 4.7^2 + m(9.8)(3.8)
V^2=44+37
v= 9m/s

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bobpursley
2. his mass has nothing to do with it.
Vi = 4.7
how long to reach top?
v = Vi - g t
0 = 4.7 - 9.81 t
t = .479 seconds up
H = 3.8 + Vi t - 4.9 t^2
h = 3.8 + 4.7(.479) - 4.9 (.479^2)
h = 3.8 + 2.25 - 1.12
h = 4.93 meters stopped above ground, falls from there
4.93 = 4.9 t^2
t = 1 second fall from 4.93 meters
v = g t = 9.81 * 1 = 9.81 m/s

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3. which one of you are correct?

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2. 👎

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