VAriable forces question (dynamics)

[Chavi]

Can I please get some help with this question (Essential Ch 13E, q13):
13. A body of mass m is projected vertically upwards with speed u. Air resistance is equal to k times the sqaure of the speed where k i s constant. Find the max height reached and the speed when next at the point of projection.
Answer: Max height = m/2k x ln(1+ku^2/mg)
Speed = u x sqrt(mg/(ku^2 + mg))

Thanks.

[itolduso]

http://www.itute.com/2008/10/20/free-download-2006-2009-specialist-mathematics-unit-3-4-kinematics-mechanics-reference-notepad/

A worked solution appears in 2/3 last page from memory.

[jasoN-]

This is just another source if itute is too discrete (actual worked solutions of the book)

[98.40_for_sure]

Lol i remember this question... frickin tedious as. took ages

[theuncle]

Can someone explain why I'm getting the wrong expression for dx/dv by doing this?




thanks