(a) Find a differential equation to model the velocity v of a falling mass m as a function of time. Assume that air resistance is proportional to the instantaneous velocity, with a constant of proportionality k > 0 (this is called the drag coefficient). Take the downward direction to be positive. (b) Solve the differential equation subject to the initial condition v(t = 0) = vo. (c) Determine the terminal velocity of the mass.

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Need help with part C. 

(a) Find a differential equation to model the velocity v of a falling mass m as a function of
time. Assume that air resistance is proportional to the instantaneous velocity, with a
constant of proportionality k > 0 (this is called the drag coefficient). Take the downward
direction to be positive.
(b) Solve the differential equation subject to the initial condition v(t = 0) = vo.
(c) Determine the terminal velocity of the mass.
Transcribed Image Text:(a) Find a differential equation to model the velocity v of a falling mass m as a function of time. Assume that air resistance is proportional to the instantaneous velocity, with a constant of proportionality k > 0 (this is called the drag coefficient). Take the downward direction to be positive. (b) Solve the differential equation subject to the initial condition v(t = 0) = vo. (c) Determine the terminal velocity of the mass.
Expert Solution
Concept and Principle:

The differential equation that represents the falling object is,

mdvdt=mgkv2dvgkmv2=dt

Integrating we get,

(mk)dv(mgk)v2=dtv(t)=mgktanh(kgmt+c2)

From part (b) we arrive at the terminal velocity equation,

v(t)=mgktanh(kgmt+tanh1kmgv0)

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