A small ball with a mass of 1 kg is thrown horizontally at an initial speed of 3 M / s, and the landing speed is 5 m / s, regardless of the resistance, g = 10 m / S ^ (1) How high is the throw point from the ground? (2) What is the instantaneous power of gravity when the ball is about to land?

(1) MGH + 1 / 2mv1 ^ 2 = 1 / 2mv2 ^ 2; V1 = 3; V2 = 5; so h = (25-9) / 20 = 0.8
(2) W = FV; this V should be the vertical component; v = 4; using Pythagorean theorem; hypotenuse = 5, horizontal side = 3, vertical side = 4
f=mg；
So w = 4

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