When the slider slides down the slope at the initial velocity V0, it is subjected to sliding friction, which can be obtained by the formula f = μ n: f = μ gcos37 = 0.8×/kloc-0 /×10× 0.8n = 6.4n, and the direction is upward along the slope.
The sliding force is equal to f ′ = mgsin37 =/kloc-0 /×10× 0.6n = 6n < 6.4n, so when the slider speed is zero, the static friction on the slider is 6n, and the direction is upward along the inclined plane. Therefore, A is correct.