A rubber ball of mass m is dropped from a cliff. As theball falls. it is subject to air drag (a resistive force caused bythe air). The drag force on t

Ayaana Buck

Ayaana Buck

Answered question

2020-12-29

A rubber ball of mass m is dropped from a cliff. As theball falls. it is subject to air drag (a resistive force caused bythe air). The drag force on the ball has magnitude bv2, where b is a canstant drag coefficient andv is the instantaneous speed of the ball. The dragcoefficient b is directly proportional to the cross-sectional areaof the ball and the density of the air and does not depend on themass of the ball. As the ball falls, its speedapproaches a constant value called the terminal speed.
a. Write, but do Not solve, a differentialequation for the instantaneous speed v of the ball in terms of timet, the given quantities quantities, and fundamentalconstants.
b. Determine the terminal speed vt interms of the given quantities and fundamental constants.
c. Detemine the energy dissipated by the dragforce during the fall if the ball is released at height h andreaches its reminal speed before hitting the ground, in terms ofthe given quantities and fundamental constants.

Answer & Explanation

unett

unett

Skilled2020-12-30Added 119 answers

σF=ma
wFη=ma
mgbv2=ma
mgkAρv2=ma where k is the proportionalityconstant
a=dvdt=g(kAρm)v2
dvdt+kAρmv2=g
I don't know if this is correct. The derivativeis with respect to time t, but is it considered "in terms oftime t?"
(b) When the terminal velocity is reached,there is no acceleration
mgkAρv2=ma=0
 v=mgkAρ

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