(1) When the slider moves from A to B, let the friction work be Wf. According to the kinetic energy theorem,

mgR+Wf= 12mv2？ 0

Solution: wf =-1.5j.

(2) If the pressure of the track on the slider is F, the resultant force of the track supporting force and gravity on the small slider at point B provides the centripetal force of circular motion.

f？ mg=mv2R

Have to? F=4.5N

According to Newton's third law, the pressure of the slider on the track is f ′ = F'= F'= F = 4.5N

(3) The slider moves horizontally after leaving B, and the landing speed is set to v'. have

mgh = 12mv’2？ 12mv2

Get v' = 52m/s.

Let the angle between V' and the horizontal plane be θ, as shown in the figure.

cosθ= vv′= 22

∴θ=45

Answer: (1) When the small slider moves along the arc trajectory, the work done by friction is-1.5j;

(2) When the small slider passes through point B, the pressure on the circular track is 4.5N；;

(3) When the small slider touches the ground, the speed is 52m/s, and the direction makes an angle of 45 with the horizontal plane.