(9)A just moves in a straight line at a uniform speed on the horizontal ground, and the sliding friction is equal to the thrust, that is

f=F9=26N

μ=fFN=F9mg=266q=q.6

(2) After combining gravity and upward thrust, vertically decompose the resultant force of gravity and upward thrust along the inclined plane to obtain:

Parallel inclined plane direction: (f-mg) colθ-f = ma;

Vertical slope direction: fn = (f-mg) linθ;

Where: f=μFN

Solution: a=9m/l2

x=92at2

The solution is t=2l.

Answer: (9) The dynamic friction coefficient μ between A and the ground is q.6；;

(2) The required time is 2&; Nalp length