1) A 1.4 kg falling object (subject to the effects of aerodynamic drag) is 1800
ID: 1776742 • Letter: 1
Question
1) A 1.4 kg falling object (subject to the effects of aerodynamic drag) is 1800 m high, traveling at 34 m/s and has not yet reached terminal speed. It first reaches terminal speed at a height of 1340 m and the terminal speed is 37.3 m/s. a) Determine if the mechanical energy (E = K + Uo) of the system consisting of the falling object and Earth's gravity field has been conserved during the fall from 1800 m to 500 m. b) How much work (if any) including the correct sign (+ or -) has been done on the system over this interval (presumably by the external drag force)? c) Will the energy of the system consisting of the object, the gravity field and the surrounding air be conserved over this interval? Explain your answer. Is there an additional energy that must be accounted for in this analysis? What is it and how much of it has been generated? Note: terminal speed is a constant speed.Explanation / Answer
1. Ei = PEi + KEi = (1.4 x 9.8 x 1800) + (1.4 34^2 / 2)
= 25505.2 J
Ef = (1.4 x 9.8 x 1340) + (1.4 x 37.3^2 / 2)
Ef = 19359 J
Ef is not equal to Ei.
so energy is not conserved.
(b) W = Ef - Ei = - 6147 J
(c) Energy will be lost against air friction.
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