Correct Answer - D
A small …………..
The friction force coin just before coin is to slip will be : `f = mu_(s) mg`
Normal reaction on the coin , `N = mg`
The resultant reaction by disk to the coin is
`= sqrt(N^(2)+f^(2))`
`= sqrt((mg)^(2)+mu_(s)^(2)(mg)^(2)) = mg sqrt(1+mu^(2))`
`= 40xx10^(-3)xx10xx sqrt(1+(9)/(16)) = 0.5 N`