My heart was beating fast when I start to make the speech. I had prepared very good but it was the first time for me to speak to so many student in the public. So I was very nervous when I began to speak. Luckily, the whole room was so quietly that I could easily make myself hear. After a while I became confident than before. Everyone listened carefully. I could see from our eyes that I was doing a good job. As soon as I finished speak, the students applauded. How an unforgettable experience!
时），θ与动力系数μ分别为（）。