题目

一质量为m=40 kg的小孩站在电梯内的体重计上.电梯从t=0时刻由静止开始上升，在0到6 s内体重计示数F的变化如图4-7-10所示.试问：在这段时间内电梯上升的高度是多少？取重力加速度g=10 m/s2. 图4-7-10 答案：思路解析：因为电梯处于上升状态,所以0—2秒内加速上升a1==1 m/s2;2—5秒匀速上升5—6秒内减速上升a2==-2 m/s2在2秒末时刻电梯速度v1=a1t1=1 m/s2×2 s=2 m/ss1=a1t12=×1×22 m=2 m2—5秒内匀速上升s2=v1·t2=2 m/s×3 s=6 m在5—6秒内匀减速运动s3=v1t3+12a2t32=2×1 m-×2×1 m=1 m所以s总=s1+s2+s3=2 m+6 m+1 m=9 m.阅读理解。One moment it was quiet and calm in the forest, the next, the air was charged with tension.The elephant had heard the distant alarm calls of animals and her mood suddenly changed.I urged the elephant deeper into the forest.We sounded like a forest fire — crackling, snapping, trailblazing.But through all the noise came a sharp warning cry.The elephant stopped and we heard it again — the tell?tale call of a spotted deer.I looked quickly around the shadows of the forest.Rays of sunlight shone through tree branches, beneath which the patchwork (交错) of green plants and shadows?within?shadows would make tiger stripes (条纹) look more attractive.Apart from an occasional noise from the elephant's stomach, the forest was silent.Gradually, the tension slipped from our bodies.The elephant seized a nearby branch and put it into her mouth.I reached forward and gently moved my hand over the elephant's neck; there was a soft part, free of wrinkles and hairs, behind her ear.This was my fourth time to_sense_the_aura of the forest in Corbett, although I saw no tigers in the end.Located at the foot of the Himalayan mountains, Corbett is home to about 135 Bengal tigers, but the forest seemed to be guarding their whereabouts (出没处), a silent reminder of their secrecy and rarity.Still, I was happy enough touching the elephant behind the ear.If I had so desperately wanted to see a tiger, I could have gone to a zoo.After all, spotting tigers merely confirms their beauty; tracking them can make you aware of something more.1.Which of the following was a clear signal of alarm?A.The elephant stopped.B.A spotted deer called.C.The elephant seized a branch.D.The forest was silent for a while.2.The author begins his account of the tour in the forest mainly by________.A.describing various soundsB.comparing different animalsC.listing different activitiesD.introducing various plants3.What does the underlined part “to sense the aura” in Para.4 most probably mean?A.To see the diversity.B.To enjoy the scenery.C.To feel the atmosphere.D.To experience the freedom.4.How does the author feel after several visits to Corbett?A.Seeing a Bengal tiger is quite thrilling.B.It is very time?consuming to travel in Corbett.C.It is really worthwhile to study the animals in Corbett.D.The process of finding Bengal tigers is most appealing.