Posted by colin on September 03, 2002 at 13:30:50:
In Reply to: Re: DE word problem posted by Brad Paul on September 03, 2002 at 13:03:50:
: : A body with mass m is projected vertically downward with initial velocity v0 in a medium offering resistance proportional to the square root of the magnitude of the velocity. Find the relation between the velocity v and the time t.
: : Do I solve for v or t here? How can I tell?
: This is an F=ma problem:
: 1) Pick a positive direction. How about positive is down.
: 2) Draw a force diagram mg points down and f sqrt(v) points up.
: 3) Sum the forces and set equal to ma
: 4) m g - f sqrt(v) = m a
: 5) Note that a=(dv)/(dt)
: 6) rewrite :
: (dv)/(dt)=g-(f sqrt(v))/m
: 7) Solve with vo at t=0
Thank you... In the book, they show the solution solved for t, not v. I'm confused about why they solved for t not v. Was there any clue in the initial problem statement?
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