(1) 物体在斜面上恰能匀速下滑，平行于斜面方向上的合力为零，则
mgsin30°=
μmgcos30° ①
μ=
="0.58··························································" ②
(2) 设物体从
A→
B的运动过程中加速度大小为
a1，
B→
C的运动过程中加速度大小为
a2，则
F－
μmg＝
ma1··············································· ③
μmg＝
ma2··················································· ④
解得
a1＝
m / s
2······································ ⑤
a2＝10
m / s
2⑥
根据题意有
，
····· ⑦
所以
········································· ⑧
sAB＝10 m···················································· ⑨
评分标准：本题共12分，其中①③④式各2分，②⑤⑥⑦⑧⑨式各1分。
