# Homework Help: Overimposed movement with friction

1. Apr 8, 2009

### Akrobit

1. The problem statement, all variables and given/known data
I need to describe a glider movement during tow. The tow is based on a single axis displacement (x) with constant speed Ps=5 m/s. The cable length is constant=50 m.. The glider area A, lift and drag coefficients (Cl and Cd) are known as a function of tangential speed (Vt).
The frictional coefficients of the tow line (Cdline) can be known as a function of local velocity. The diameter of the line is known=Ldiam. Y axis is vertical and the problem can be considered to develop only on the X-Y plane. The starting line angle (alpha) respect to x axis of the movement can be about 20º. The nonconservative force (Px) pulling the tow line along the x axis is the only external input energy.
Vt= tangential speed of glider
d=density of air
Ar=aspect ratio of glider wing
Cd0=coefficient rapresentative of other glider drag components proportional to square tangential velocity
Vlocal is the cvelocity of a certaion point of the tow line
The goal is to obtain an expresion for Vt and(or) alpha as a function of the other parameters

2. Relevant equations
Lift of the glider L=Cl(Vt)*d/2*Vt^2*A
Drag of the glider D=(Cd(Vt)+Cl(Vt)^2/pi/Ar+Cd0)*d/2*Vt^2*A
Drag coefficient for the line Cdline:3/log10(Reline)
Reline=65535*Ldiam*Vlocal

3. The attempt at a solution