Free Fall with Air Resistence

ma = F = mg - c v
my” = mg - c y’
y” + (c/m) y’ = g

Clear[m,c, g]
eqn=y''[t]+(c/m) y'[t]==g

DSolve[{eqn,y[0]==0,y'[0]==0},y[t],t]

Expand[%]

y(t) = (gm^2)/(c^2) [1 - (e^(-ct/m))] + gmt/c

sol=DSolve[{eqn,y[0]==0,y'[0]==0},y,t]

yf=sol[[1]]

pos[t_]:=y[t] /. yf

vol[t_]:=y'[t] /.yf

m=1; c=0.8; g=0.98;
pos[1]

Plot[{pos[t] ,vol[t]}, {t,0,5},AxesLabel->{time,position},PlotLegends->"Expressions"]