
The point A covers 30∘ in 0.1s.
Then, we have 6πrad⟶0.1s.
Or 1rad⟶6π0.1s
Or 2πin→π0.1×6×2π
Thus, time taken is T=1.2sec.
We know that ω=T2π
Then, ω=1.22π
Restoration force (F)=mω2A.
Then Restoration force per unit mass (mF)=ω2A
(mF)=(1.22π)2×0.36
≅9.87N