Cats on a Roof

Friction resists movement, and M (mu) is the friction coefficient. The force of friction is directly related to mu, so a smaller mu causes the force of friction to be smaller. A large friction force is keeping the white cat from moving on the roof, so the white cat has a large mu. The brown cat has a small mu because it is sliding on the roof, so there is a small friction force which is why the brown cat falls first.