题目

阅读理解Of all nature's disasters, forest firesare often considered the most frightening. Moving at lightning speed, hugewalls of flames can burn acres of land in just a few minutes. And althoughtechnology, including the use of fire­retardant chemicals, hasgreatly helped the fight against forest fires, they still take great damage. According to the National InteragencyFire Center, the fire season last year was the worst on record in terms of thenumber of fires and acres(公顷) burned. There were96, 385 fires and 9, 873, 429 acres affected by fire in a year that was 125%more destructive (如图所示，木块的质量m = 2 kg，与地面间的动摩擦因数μ= 0.2，木块在拉力F=10N作用下，在水平地面上向右做匀加速直线运动，经3s时间撤去外力F．已知力F与水平方向的夹角θ= 37°，sinθ=0.6，cosθ=0.8，g 取 10 m/s2．试问：（1）撤去外力前，物体运动的加速度大小（2）刚撤去外力时，物体运动的速度（3）撤去外力后，到停止滑行的距离