On a rough inclined plane. The force between two blocks is zero if:
- !!mu_1 > mu_2!!
- !!mu_1 < mu_2!!
- !!mu_1=mu_2!! Solution
The only possible way there is force between the two is if the !!m_2!! is moving slowly than !!m_1!!.
We assume that they start from rest, so they have same initial velocity, so everything comes down to just acceleration since !!v=u+at!!
The acceleration of any block on the inclined plane is given by !!a = gsintheta-mugcostheta!!
So the relation would be !!gsintheta-mu\1gcostheta<=gsintheta-mu\2gcostheta!!
So !!A, C!!