Thanks very much for the help.

Thanks very much for the help.

@Carl Love i am supose to look at two difrent plots one for earth and one for venus. so i cant change the top parameters. then i will only have one of the plots. i know i can copy paste and have the same thing two times but that is just a mess 

@Preben Alsholm thanks for the help it helped a bit but can not find the way out of it still. the task was to find a table of the ball's range as a function of the starting rate for a v_0 ranging from 0.2 .. 4.0 with 0.2 m/s increase in each step. where the throw angle is 36 degrees. then i should plott all the castes on one plott. 

C_0:=0.4: d:=0.0002: mu:=1.8*10^(-5): rho:=1.2: g:= 9.81:
rho_v:=1000.0: m:=evalf((4/3)*Pi*rho_v*(d/2)^3):

F_D:=proc(v::list) # kraft/masse
local k,vx,vy;
vx:=v[1];
vy:=v[2];
k:=evalf((3*Pi*mu*d+(Pi/8)*C_0*rho*(d^2)*sqrt(vx^2+vy^2))/m);
[k*vx,k*vy];
end proc;

Eskritt:=proc(vo::list,h)
local vx,vy, F;
F:=F_D(vo);
vx:=vo[1]+h*F[1];
vy:=vo[2]+h*(F[2]-g);
[vx,vy];
end proc;

From here i dont realy know what to do

phi:=Pi/5: v0:=evalf([v_0*cos(phi), v_0*sin(phi)]): v[0]:=v0;
h:=0.002: N:=150:
for i from 0 to 19 do
v_0:=0.2+i*0.2:
end do:

for i from 1 to N do
v[i]:=Eskritt(v[i-1],h);
end do:

diff('r'(t),t)='v'(t);

r[0]:=[0,0]:

for i from 1 to N do
r[i]:=r[i-1]+h*v[i-1];
end do:

r[i+1];