. A bird is flying with a speed of 18.0 m/s over water when it accidentally drops a 2.00 kg fish. If the altitude of the bird is 5.40m and friction is disregarded, what is the speed of the fish when it hits the water?

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mathssydney mathssydney · Answer 1 · 2016-12-12T17:47:09-05:00

v^2 = u^2 + 2gr, where v - speed, u - initial speed=0, r - displacement (or height)
v^2 = 0 + 2105.4
v = 10.2 m/s

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jbiain jbiain · Answer 2 · 2020-01-23T07:34:19-05:00

Answer:

20.73 m/s

Explanation:

Defining as state 1 the moment before the drop and state 2 the moment when the fish hits the water. Then:

speed at state 1, v1 = 18.0 m/s

mass of the fish, m = 2.00 kg

height at state 1, h1 = 5.40 m

height at state 2, h2 = 0 m

speed at state 2, v2 = ? m/s

acceleration of gravity, g = 9.8 m/(s^2)

We know that the addition of kinetic energy (1/2mv^2) and potential energy (mgh) at both states must be equal. Then:

1/2mv1^2 + mgh1 = 1/2mv2^2 + mgh2

Replacing with data (units are omitted):

1/2218^2 + 29.815.4 = 1/22v2^2 + 29.810

430 = v2^2

v2 = √430

v2 = 20.73 m/s