The physics
When a crate slides, kinetic friction acts against the sliding. On a flat floor, its size is μkmg. So the crate slows down at μkg, whatever its mass.
a = μk g d = u² / (2 μk g) t = u / (μk g)
Static friction holds a crate still up to a limit, μN. A rope at angle α lifts the crate a little. That makes N smaller, so the limit gets smaller too.
least pull: F = μmg / (cos α + μ sin α) best angle: tan α = μ
Friction turns the lost motion into heat. Over a skid d, the heat is μmgd.