We can choose any arbitrary directions of frictional forces at different contacts
In the final answer, the negative value will show the opposite directions.
Let f1= friction between plank and cylinder
f2= friction between cylinder and ground
a1= acceleration of plank
a2= acceleration of centre of mass of cylinder and α angular acceleration of cylinder about is
COM. Directions of f1 and f2 are as shown here
Since, there is no slipping anywhere ∴a1=2a2 .......(i)
(Acceleration ofplank = acceleration oflop point of cylinder)
a1=F−f1m2.......(ii)
a2=f1+f2m1.......(iii)
α=(f1−f2)RI
(I= moment of inertia of cylinder-about COM)
∴α=(f1−f2)R12m1R2
α=2(f1−f2)R12m1R.....(iv)
α=2(f1−f2)m1 .....(v)
(Acceleration of bottommost point of cylinder =0)
a) Solving Eqs, (i), (ii), (iii) and (v), we get
a1=8F3m1+8m2
and a2=4F3m1+8m2