enter code here 
m1 := 0.04 (*Hi all, this message keeps on popping up even though I think I have defined every single variable numerically. Are there other possible reasons? Thank you*)
m2 := 14
g := -9.81 
l1 := 1/4.75 
l2 := 3.75/4.75
lb := 1/2 - l1
lambda := 1/10
mb := lambda*Sqrt (m1)*(l1 + l2)
Ib := 1
ls := 1
dmax := ((2 + Sqrt[2])/m2)*(m1*l1 - mb*lb)
e := dbest/dmax
dphi := phib[t] - phis[t]
alphab := (m2*l2*ls)/(m1*l1^2 + m2*l2^2 + mb*lb^2 + Ib)
omegabsquared := 
 g*(m1*l1 - m2*l2 - mb*lb)/(m1*l1^2 + m2*l2^2 + mb*lb^2 + Ib)
alphas := l2/ls
omegassquared := g/ls
s := NDSolve[{phis''[t] == 
    alphas*((phib'[t])^2*Sin[-dphi] + phib''[t]*Cos[-dphi]) - 
     omegassquared*Sin[phis[t]], 
   phib''[t] == 
    alphab*((phis'[t])^2*Sin[dphi] + phis''[t]*Cos[dphi]) - 
     omegabsquared*Sin[phib[t]], phis[0] == Pi/2, phib[0] == 3*Pi/4, 
   phis'[0] == 0, phib'[0] == 0}, {phib[t], phis[t]}, {t, 0, 100}]
s