题目

When it comes to public speaking, the most important thing is to speak clearly. You want the audience   61   (hear) everything you have to say when giving public speeches, not to question your words later   62  they couldn’t hear you. A good public speaker is the person who knows           63  to speak clearly. Practice   64   (make) perfect. Try practicing in front of a mirror, in front of your friends, or even in front of your pet dogs if you need help.    65   (use) the proper tone when speaking. Most people find it easy to slip into a monotone voice, 汽车刹车前以10m/s的速度行驶，刹车后以大小为2m/s2的加速度做匀减速直线运动，求：（1）汽车的刹车时间为多少？（2）刹车后汽车4s内通过的位移是多少？