题目

如图3-5-10所示，气球重10 N，空气对其浮力为16 N.由于受水平方向的风力的影响，系气球的绳子与水平面成θ＝60°角.由此可知，绳子的拉力大小为___________N，水平方向的风力大小为_______________N. 图3-5-10 答案：6.928  3.46 解析:把绳子拉力正交分解得，水平方向Tcos60°=F风，竖直方向 Tsin60°+mg=F浮，代入数据联立解得：T=4 N=6.928 N,F风=3.46 N.During my travels through the mountains of Greece I was only ever scared once. It was dusk and as I walked alone I came across six large wolves（狼）that were feeding on the body of a dead animal. I had heard many stories about wolves as a child and it was this animal that I feared more than any other. The wolves before me were huge, at least 6 feet long and covered with thick grey fur. As I went near, the wolves left the blood-covered snow that surrounded the body and started walking towards me, one after another. They stopped about 20 metres from me and stared. The lead wolf raised his head into the air and took in a deep breath, as if he was smelling my presence. The animals looked both beautiful and frightening, but I knew I could not show them my fear. As I drew nearer, the lead wolf raised its head once more but this time let out a long, loud cry. The awful cry rang out across the silent valley. I had never heard a more frightening sound. I was almost certain it was a sign to be death. Every moment I expected to see the pack of wolves dash（冲）at me. I knew my only hope was to pretend I had no fear. I walked past the line of wolves, like a general（将军）moving among his soldiers. They cried out loud again. But when they saw that their cry did not cause me to change my direction or make me run they feared to come after me, so they let me pass and returned to the dead animal. If I had turned back or tried to run away when they marched out to meet me, I am certain the whole pack would have attacked（进攻）me in a moment. But my show of false courage intimidated them and kept them back. 64. Why didn’t the wolves attack the man? A. They were no longer hungry when they saw him. B. The man was already known to the wolves. C. They were too far away to catch the man. D. The man showed no fear as he passed by. 65. The underlined word “ intimidated” in the last paragraph probably means “         ”. A. encouraged             B. scared                     C. doubted                        D. hurt 66. What is the author’s intention in writing this story? A. To show that mountains can be dangerous places. B. To discuss the habits of mountain wolves. C. To make people aware of the danger of wolves.       D. To stress the need for courage when in danger. 67. Which is the best title for this story? A. In Face of Fear                                               B. My Trip to Greece C. My Mountain Travels                                 D. A Man Without Fear