题目

阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。With my high school life 【1】 ( begin) , I feel a little anxious right now. I hope to make a good first 【2】 (impress). But I wonder whether I will make friends or what if no one 【3】(talk) to me.To tell the truth, the maths class was difficult for me, 【4】 the teacher was kind and friendly. He told 【5】 ( we )a funny story and every student laughed so much! In the afternoon, we had our chemistry class in the science lab. The lab is new and the lesson was 【6】( interest) , but the gu有一质量为m=2Kg的物体静止于水平面上的D点，水平面BC与倾角为θ=370的传送带AB平滑连接，转轮逆时针转动且传送带速度为v=1.8m/s，物体与水平面间的动摩擦因数为μ1=0.6，物体与传送带间的动摩擦因数为μ2=0.8。DB距离为L1=48m，传送带AB长度为L2=5.15m。在t=0s时，将一水平向左的恒力F=20N作用在该物体上， 4s后撤去该力。（sin37°＝0.6，cos37°＝0.8，g=10m/s2）求：（1）拉力F作用在该物体上时，物体在水平面上运动的加速度大小？（2）物体到达B点时的速度大小？（3）物体从D点到A点运动的总时间为多少？